The Semantic Web 2 sessions in the Module INF347 at the École nationale supérieure des Télécommunications in Paris/France in Summer 2011 by Fabian M. Suchanek This document is available under a Creative Commons Attribution Non-Commercial License
The Semantic Web 2 sessions in the Module INF347 at the École nationale supérieure des Télécommunications in Paris/France in Summer 2011 by Fabian M. Suchanek.
Dec 26, 2015
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The Semantic Web
2 sessions in the Module INF347at the Eacutecole nationale supeacuterieure des Teacuteleacutecommunications
in ParisFrance in Summer 2011
by Fabian M Suchanek
This document is available under aCreative Commons Attribution Non-Commercial License
2
Organisation
bull 2 sessions (each 15h) on the Semantic Web
bull 15h lab session
bull Web-siteshttpwwwinfresenstfr~danzartINF347
httpsuchanekname Teaching
3
MotivationIn the last class on Information Extraction we saw how to move from unstructured data to structured data
Person
Job
Elvis singer
But even between structured data interaction is difficult
Person
Occupation
Elvis P singer
ltxmlgt ltpersongt ltoccupationgt singer
4
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
5
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
2
Organisation
bull 2 sessions (each 15h) on the Semantic Web
bull 15h lab session
bull Web-siteshttpwwwinfresenstfr~danzartINF347
httpsuchanekname Teaching
3
MotivationIn the last class on Information Extraction we saw how to move from unstructured data to structured data
Person
Job
Elvis singer
But even between structured data interaction is difficult
Person
Occupation
Elvis P singer
ltxmlgt ltpersongt ltoccupationgt singer
4
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
5
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
3
MotivationIn the last class on Information Extraction we saw how to move from unstructured data to structured data
Person
Job
Elvis singer
But even between structured data interaction is difficult
Person
Occupation
Elvis P singer
ltxmlgt ltpersongt ltoccupationgt singer
4
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
5
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
4
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
5
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
5
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
6
Motivation
Person
Job
Elvis singer
But even between structured data interaction is difficult in particular if the data is in different formats on different machines or devices or in different companies
ltxmlgt ltpersongt ltoccupationgt singer
Person
Occupation
Elvis P singer
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
7
Use casesExamplesbull Booking a flight Interaction between office computer flight company travel agency shuttle services hotel my calendar
bull Finding a restaurant Interaction between mobile device map service
recommendation service restaurant reservation service
bull Web search Interaction between client search service
Web page content provider
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
Use cases
8
bull Intelligent home Fridge knows my calendar orders food if I am planning a dinner
bull Intelligent cars Car knows my schedule where and when to get gas how not to hit other cars what are the legal regulations
bull Web service composition Interaction between client and Web services and
Web services themselves
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
9
MergingExamplesbull Adding data to a database From XML files from other databases
bull Merging data after company mergers (eg Apple buys Microsoft) Different terminology has to be bridged accounts to be merged
bull Merging data in research eg biochemical genetic pharmaceutical research data
(Less exciting but probably more frequent)
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
10
The Semantic Web
Idea We need an infrastructure that allows computers to ldquounderstandrdquo their data
This infrastructure shallbull allow machines to process data from other machinesbull ensure interoperability between different schemas
devices and organizationsbull allow data to describe databull allow machines to reason on the databull allow machines to answer semantic queries
This is what the Semantic Web aims at
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
11
The Semantic Web
The Semantic Web is an evolving extension of the World Wide Web in which data is made available in one standardized semantic format
hellip we will learn more about this format in a minute
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
12
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data1935
singer
born
Elvis where are you
born
bull Publish data (RDFa)
Ontology
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
13
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
Standards produced byor endorsed by theWord Wide Web Consortium(W3C)
represented in Europeby the European Research Consortium for Informatics and Mathematics (ERCIM) with INRIA being a member
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
14
URIsGoal Identify entities uniquely worldwideThe same entity can have multiple identifiers but the same identifier shall always mean the same entity
Elvis
Elvis
Elvis Presley
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
15
URIsA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
httpimitatorsorgElvisFG17
httpelvisorgme
httpontocompeoplesingersEP
A URI can take the form of a URL
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
16
URIs and URLs
httpelvisorgme Identifies the person not Internet-accessible
httpelvisorgindexhtml Identifies a fileInternet-accessible
Age
76
5
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
17
NamespaceshttpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
The domain provides a ldquonamespacerdquo ie a range of identifiers that cannot collide with other
identifiers
httpimitatorsorgElvis hellip
httpelvisorgElvis
httpimitatorsorgMadonna
httpholyorgMadonna
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
18
URI Use Cases
There should be no URI with two meanings
People can invent all kinds of URIsbull a company can create URIs to identify its productsbull an organization can assign sub-domains and each sub-domain can define URIsbull individual people can create URIs from their homepagebull people can create URIs from any URL for which they have exclusive rights to create URIs
httpimitatorsorgElvisFG17
World-wide uniquemapping to domain owner
in the responsibilityof the domain owner
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
19
URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
The IANA (Internet Assigned Numbers Authority) operated by ICANN assigns namespaces to specific organizations
The organization then specifies the identifier
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
20
Example URNsA Uniform Resource Name (URN) is a URI that is globally assigned
A URN takes the form
ldquournrdquo + Namespace + ldquordquo + Identifier
urnisbn123456789
Example
Identifier assigned by ISO to a book
Namespace assigned by IANA to the International Standards Organization (ISO)
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
21
Example URNs
bull ISBN urnisbn1234567bull ISAN urnisan0000-1111-2222-3333-4444bull SWIFT urnswiftbicBYLADEM1000bull OID urnoid216840
examples arehypothetical
Example
Object IDs identifiers form one global tree of identifiers where sub-trees are administrated by authoritiesFor example the IANA administrates ids for companies
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
22
UUIDs
bull UUID urnuuid6e8bc430-9c3a-11d9-9669-0800200c9a66
A Universally Unique ID (UUID) is a software-generated string that is globally unique
Computed eg by using bull the MAC address (identifier of the computer)bull plus a timestamp
Example run ifconfig getmac
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
23
URIs SummaryA Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet
The goal is to give ldquoall things on Earthrdquo a unique identifier
Two main approaches1 URL-like identifiers2 Uniform Resource Names (URNs)
URNs URLs
URIs
Propose another real-world domain where we could establish URNs
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
24
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
25
RDFThe Resource Description Framework (RDF) is a standardizedknowledge representation model that resembles the entity-relationship model
An RDF statement (triple) is a triple of 3 URIs calledthe subject the predicate and the object
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
26
RDF
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
identifies identifies
the relationship of winning something
identifies
Grammy Award
ldquoElvis won the Grammy Awardrdquo
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
27
RDF Graphs
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
Elvis Presley
won
Grammy Award
A set of RDF statements is isomorphic to a labeled directed multi-graph which is the notation we will use here
The subject and object of a triple correspond to nodesthe predicate corresponds to directed edge from subject to object with a label given by the predicate
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
28
Sample RDF Graph Example Elvis in YAGO
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
29
Namespace PrefixesA namespace prefix is an abbreviation for the prefix of a URI
elvishimself inriawon grammyprize
prefix elvis httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
A URI abbreviated this way is called a qname
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
30
Default Prefix
himself inriawon grammyprize
prefix httpelvisorgprefix inria httpinriafrrdfdtaprefix grammy httpg-acom
httpelvisorghimself httpinriafrrdfdtawon httpg-acomprize
The default namespace prefix is just a colon In the following we assume such a prefix
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
31
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize
Elvis Grammy Award
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
32
Tabular Data in RDF
GrammyAward
All tabular data can be expressed in RDF
won
Person
Prize Country
Elvis Grammy Award USA
USA
isFrom
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
33
Event EntitiesAll tabular data can be expressed in RDF
Person
Prize Year
Elvis Grammy Award 1967
GrammyAward
1967
Event42 year
prize
person
Event42
Event entities are artificial entities that representa complex constellation
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
RDF Semantics
GrammyAwardwon
NatAcademypresents
A triple ltspogt is interpreted as a First Order Logic fact p(so)
won(Elvis GrammyAward)presents(NatAcademy GrammyAward)
34
The triple of URIs ltspogt the graph and the First Order Logic fact are equivalent representations of the same statement
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
Notation 3
35
Notation 3 (N3) is a concrete syntax for RDF
prefix lthttpinriafrgt prefix elvis lthttpelvisorggt
NatAcademy presents lthttpg-acomprizegt
elvishimself won lthttpg-acomprizegt plays ltguitargt
Qnames or URIs
Same subject can be abbreviated
GrammyAwardwon
NatAcademypresents
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
RDF XML Syntax
36
RDF can also be stored in XML format
ltxml version=10gtltrdfRDF xmlnsrdf=ldquohttpwwww3orgnsrdquo xmlnsi=ldquohttpinriafrrdfdtardquogt
ltrdfDescription rdfabout=ldquohttpelvisorghimselfrdquogt ltiwon rdfresource=ldquohttpAwardldquo gt ltrdfDescriptiongt
Properties of X are listed inside an rdfDescription about=X
GrammyAwardwon
NatAcademypresents
Namespaces become XML namespaces
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
RDF Concrete Syntax
37
RDF can also in a database
Subject Predicate
Object
httpelvisorghimself
won httpg-acomprize
GrammyAwardwon
NatAcademypresents
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
38
Labels
ldquoElvisrdquo ldquoThe Kingrdquo
rdfslabelrdfslabel
A label is a human-readable name for an entity
Synonymy Two labels share the same entity
Ambiguity One label refers
to different entities
Find 1 example for synonymyand 1 example for ambiguity
Another namespacewhich we will see later
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
39
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
40
ClassesA class (also called concept) can be understood as a set of similar entities
person
singer
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
41
Classes in RDF
person
singer
The fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
42
Classes in RDFThe fact that an entity belongs to a class is expressed by the type predicate from the standard namespace rdf (httpw3corg )
rdftype
The fact that a class is a sub-class of another class is expressed by thesubclassOf predicate from the standard namespace rdfs (httpw3corg )
person
rdfssubclassOf
singer
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
43
Taxonomy
singer
rdftype
A taxonomy is a hierarchy of classes
person
Resource
rdfssubclassOf
rdfssubclassOf
unemployed
rdftype
theory
abstraction
rdftype
rdfssubclassOf
taxo
nom
yin
stan
ces
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
44
Taxonomy
singer
rdftype
person
rdfsResource
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
The most general class is rdfsResource ndash everything is a resource
More special class
More general class
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
45
Taxonomy
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
taxo
nom
yin
stan
ces
Y is a class if we can say ldquoX is a Yrdquo
X is a sub-class of Y if we can say ldquoEvery X is a Yrdquo
Everything else is an instance (of a particular class)
Make a taxonomy of animals
Include at least 2 instances
rdfsResource
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
46
SubclassOf Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOfltXsubclassOfYgtltYsubclassOfZgt
ltXsubclassOfZgt
Every class is a subclass of all more general classes
rdfssubclassOfrdfsResource
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
51
RDFS Semantics
singer
rdftype
person
rdfssubclassOf
rdfssubclassOf
RDFS specifies 44 entailment rules of the form
If the graph contains these triples
then the graph contains this triple
The entailment rules are appliedrecursively until the graph doesnot change any more
The result is called the deductive closure
rdfssubclassOfrdfsResource
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
53
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
54
Storing dataRDF data is usually stored on a server (=internet accessible computer)
gGrammy Award
gPrize
rdftype
gNatAcademy
gpresents
Namespaceg = httpg-acom
prefix g httpg-acom prefix rdf httpwwww3org
gGrammyAward rdftype gAward
gNatAcademy gpresents gGrammyAward
The server at httpg-acom stores
Try this
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
55
Storing data
The ontology is shown here in the graphical form but it is stored on the server in textual form
Example The YAGO ontology is stored at the server at httpmpiideyago
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
56
Cool URIsA URI is not necessarily dereferenceable (ie it cannot be accessed online)
httpg-acomGrammyAward
but it can be dereferenceable This means that if I access the URL the server responds with an RDF snippet
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
URIs can be ldquoclickedrdquo (followed)
=gt NOT FOUND
Try this out rdftype = httpwwww3org19990222-rdf-syntax-nstype
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
57
Cool URIs
prefix g httpg-acom prefix rdf httpwwww3org19990222-rdf-syntax-ns
gGrammyAward rdftype gAwardhttpelviscomelvis gwon gGrammyAward
prefix e httpelviscom prefix rdf httpwwww3org19990222-rdf-syntax-ns
eelvis rdftype esingereelvis eborn 1935
Server at httpg-acom
Server at httpelviscom
The RDF graph becomes traversable
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
58
Wersquore all one GraphIf two RDF graphs share one node they are actually 1 graph
gGrammy Award 1935
esinger
born
gPrize
ewon
rdftype
Namespacee = httpexampleorg
Namespaceg = httpg-acom
A machine can follow the links and retrieve more information in the neighboring ontology
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
59
Standard VocabularyA number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
dc Dublin Core (predicates for describing documents) httppurlorgdcelements11
foaf Friend Of A Friend (relationships between people) httpxmlnscomfoaf01
cc Creative Commons (types of licences) httpcreativecommonsorgns
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
60
Standard Vocabulary
Standard vocabulary provided by the W3Cbull type bull subclassOf bull Property bull Classbull labelbull hellip
A number of standard vocabularies have evolved
rdf The basic RDF vocabulary httpwwww3org19990222-rdf-syntax-ns
rdfs RDF Schema vocabulary httpwwww3org19990222-rdf-syntax-ns
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
61
Dublin Coredc Dublin Core (predicates for describing documents) httppurlorgdcelements11
httpelvisorgbiohtml ldquoA biography of Elvisrdquo
dcTitleFabiandcCreator
ldquoThis is the entire life ofrdquo
dcDescriptionldquoTextrdquo
dcType
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
62
Creative Commonscc Creative Commons (types of licences) httpcreativecommonsorgns
ccBYcclicense
httpfabianorg
ccAttributionUrl
ccReproductionldquoFabianrdquoccAttributionName
ccWork
ccpermits
Creative Commons is a non-profit organization which defines verypopular licenses notablybull CC-BY Free for reuse just give credit to the authorbull CC-BY-NC Free for reuse give credit non-commercial use onlybull CC-BY-ND Free for reuse give credit do not create derivative works
rdftype
Try this
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
63
Sharing FOAFfoaf Friend Of A Friend (predicates for relationships between people) httpxmlnscomfoaf01
AllShookUpfoafmadefoafknows
ldquoElvis Presleyrdquofoafname
foafPerson
Google launched httprdfdata-vocabularyorg which provides vocabulary for addresses and other personal information
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
64
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
65
The Goal of OWLRDFS just allows us to define classes and subclasses with very limited inference
Can we go further
bull Reasoning If X is left of Y and Y is left of Z then X is left of Zbull Class definitions The class of husbands is the class of married menbull Class properties People and tables are two disjoint classes
Goal of the Web Ontology Language(OWL)
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
66
OWL VocabularyOWL is a namespace that defines predicates with certain semantic rules
Man
Father
Parent
listowlIntersectionOf
rdftypeX rdftype CC owlintersectionOf LISTLIST hasElement Z
X rdftype Z
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
67
OWL UndecidabilityOWL defines so powerful predicates that it is undecidable
owloneOf
owltwoOf
owlreflexiveIntersectionOf
owlcomplicatedCombinationOf
owlhyperSymmetricProperty
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
The ldquolistrdquo is an RDF list with predicates defined there
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
68
OWL-DL GoalOWL-DL is a subset of OWL that is decidable
OWL-DL comes with a simplified notationcalled Description Logic
father = parent | | man
This notation is equivalent to the RDF graph representationWe will use the simplified notation now
Man
Father
Parent
listowlIntersectionOf
rdftype
hasElementhasElement
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
Intersection
69
X | | Y The class of things that are in both X and Y
father = parent | | malePerson
This corresponds to the First-Order Formula
x father(x) lt= gt parent(x) malePerson(x)
malePerson parent
fath
er
OWL-DL is primarily concerned with describing sets of entities
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
Union Intersection Negation
70
X | | YX | | Y~X
= (parent | | man) | | (hardRockSinger | | softRockSinger) | | ~married
= person | | ~(hardRockSinger | | softRockSinger)
person parent hardRockSinger softRockSinger happyPerson marriedPerson malePerson
unmarried-rock-singing-father
non-rock-singing-person
rockSinger = hardRockSinger| | softRockSinger
The class of things that are in X or in YThe class of things that are in both X and YThe class of things that are not in X
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
71
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
R A predicateroleC a class
has-happy-child = hasChildhappyPerson
E
This corresponds to the First Order Logic formula x has-happy-child(x) lt=gt y hasChild(xy) happyPerson(y)
hasChildhappyPerson
hasChild
hasHappyChild
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
72
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
has-only-happy-children =
hasChildhappyPerson
A
This corresponds to the First Order Logic formula x has-only-happy-children(x) lt=gt y hasChild(xy) =gt happyPerson(y)
hasChild
hasChild
happyPerson
hasHappyChild
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
73
RestrictionsRC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
singer-with-happy-child =
singer | | hasChildhappyPerson
singer-with-only-happy-children =
singer | | hasChildhappyPerson
A
E
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
74
Subclass Assertions
X | Y X is a subclass of Y (everything in X is also in Y)
happysingers| singer | | hasChildhappyPerson
singer | person
This corresponds to the First Order Logic formula x singer(x) =gt person(x)
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
75
Type Assertionsa C a is of type C (a is in C)
elvis singer | | hasChildhappyPerson
elvis singer
This corresponds to the First Order Logic formula
singer(elvis)
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
76
Fact Assertions(XY) R X and Y stand in relationship R
(elvislisa) hasChild
This corresponds to hasChild(elvislisa)
(elvispriscilla) marriedTo
This corresponds to marriedTo(elvispriscilla)
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
77
Exercise
RC The class of things where all R-links lead to a CRC The class of things where there is a R-link to a C
EA
Class constructors
X | | YX | | Y~X
The class of things that are in both X and YThe class of things that are in X or in YThe class of things that are not in X
X | Y
Assertions
X is a subclass of Y (everything in X is also in Y)aC a is a thing in the class C
(ab)R a and b stand in the relation R ie R(ab)
Assume the classes male person happyPerson and the predicates marriedTo hasChild
bull build the class of married peoplebull build the class of people married to at least 1 happy persbull build the class of happy male married peoplebull say that married people are happy
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
79
Cardinality Restrictionsge n R The class of those who have more than n outgoing R linksle n R The class of those who have less than n outgoing R linkssingers with more than 10 children
singer| | ge 10 hasChild
people with exactly 10 children
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
80
Entity SetT The class of all things The empty classT
everybody has more than 10 children
ge 10 hasChild | T
nobody has more than 10 children
ge 10 hasChild |
T
People with more than 10 children are not happyPeople whose children are all male are not happy
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
82
OWL-DLOWL-DL basically reasons about properties such as
bull having a link to an element of a class
ldquoThose that have a female childrdquo
EhasChildfemale
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
83
OWL-DL
bull having all links of one type leading to a certain class
ldquoThose thathave only femalechildrenrdquo
AhasChildfemale
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
84
OWL-DL
bull having at most or at least n links of a certain type
ldquoThose thathave more than1 childrdquo
ge 2 hasChild
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
85
OWL-DL
bull being in two classes at the same time
ldquoThose thathave more than1 child and have only femalechildrenrdquo
ge 2 hasChild AhasChildfemale
X | |Y
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
86
OWL-DL
elvis hasChildfemale
AhasChildfemale
A
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class
OWL-DL basically reasons about properties such as
bull having a link to an element of a class
bull belonging to such a class
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
87
OWL-DL
bull standing in a relationship
(elvis pricilla) marriedTo
marriedTo
bull being in two classes at the same time
bull having at most or at least n links of a certain type
bull having all links of one type leading to a certain class bull having a link to an element of a class
bull belonging to such a class
OWL-DL basically reasons about properties such as
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
88
OWL-DLOWL-DL infer properties to make the knowledge baseconsistent
Whatever other children Priscilla has will become girls
AhasChildfemale
(priscilla navarone)hasChildpriscilla hasChildfemale
=gt navaronefemale
This may fail of course
navaronemalemale | | female |
T
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
89
Reasoning TasksClassical reasoning tasks in OWL-DLbull Is the knowledge base consistent
singer | person
bellosingerbellodog
dog| ~person
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
90
Reasoning Tasks
bull Is one class a subclass of another class
hasChildLisa| singer
E
(Are all parents of Lisa singers)
can be reduced to the consistency problem
(bobLisa) hasChildbob~singer
More precisely we ask Does it follow necessarily from the KB that one class is a subclass of the otherIf so we get a contradiction here
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
91
Reasoning Tasks
bull Is an individual an instance of a class
elvissinger can be reduced to the consistency problem
elvis~singer
More precisely we ask Does it follow necessarily from the KB that Elvis is a singer If so this assertion will cause a contradiction
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
92
OWL OWL-DL
bull Does an individual have a certain property
elvis singsgoodSongE
can be reduced to the consistency problemelvis ~ singsgoodSong
E
More precisely we ask Does it follow necessarily from the KB that Elvis sings at least one good song If so this assertion will cause a contradiction
bull Is an individual an instance of a class
bull Is one class a subclass of another class
Classical reasoning tasks in OWL-DLbull Is the knowledge base consistent
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
93
OWL-DL SummaryOWL-DL is a decidable subset of OWL
It is based on the description logic SHOIN(D) a formalism that allows describing properties of objectsin a manner inspired by set theory
A
hasChildfemale
There are a number of free OWL DL reasonersavailable onlinebull Pelletbull FaCT++bull Prova
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
94
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
95
SPARQLSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
Find me all the values for loc such that the triple is true
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
96
SPARQL MatchingSPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
Elvis where are you
elivesInmoon
PREFIX e lthttpelvisorggt
SELECT locWHERE eelvis elivesIn loc
elivesIn loc
loc = emoonSPARQL queries can be seenas sub-graph matching
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
97
SPARQL MatchingPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT loc xWHERE x elivesIn loc x rdftype esinger
elivesIn loc
loc = emoonx = eElvis
eGraceland
elivesIn
esinger
rdftype
x
esinger
rdftype
elivesInmoon
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
99
SPARQL Result SetsPREFIX e lthttpelvisorggt PREFIX rdf lthttpw3corggt
SELECT xWHERE x elivesIn loc
elivesIn loc
x = ePriscillax = eElvis
eGraceland
elivesIn
esinger
rdftype
xelivesIn
moon
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
103
SPARQL EndpointsMany ontologies provide a ldquoSPARQL endpointrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
httpesww3orgSparqlEndpoints
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
104
SPARQL Example
select distinct x lthttpdbpediaorgresourceElvis_Presleygt lthttpwwww3org19990222-rdf-syntax-nstypegt xlimit 100
Example at httpdbpedia-liveopenlinkswcomsparql
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
105
SPARQL SummarySPARQL (SPARQL Protocol and RDF Query Language) is the query language of the Semantic Web
PREFIX e lthttpelvisorggt PREFIX rdf httpw3corgPREFIX glthttpg-acomgt
SELECT xWHERE x ewon gGrammy
SPARQL borrows concepts from SQL but is specially adapted to distributed RDF graphs
Many ontologies provide ldquoSPARQL endpointsrdquo ie a service than canbull receive SPARQL queries sent by a machinebull receive SPARQL queries typed by a human in a Web interface
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
106
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
107
Linked Data Problem
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
Many ontologies talk about the same entity with different URIs
This is bad because we cannot join the information
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
108
Linked Data Solution
1935
guitar
born
DBpedia(httpdbpediaorg )
rdftype
Elvisopedia(httpelvisopediaorg )
singerplays
OWL provides vocabulary to link equivalent entities
httpelvisopediaorgElvis owlsameAs httpdpbediaorgElvis
owlsameAs
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
109
The Linking Data ProjectThe Linking Open Data Project aims to interlink all open RDF data sources into one gigantic RDF graph (link)
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
110
The Linked Data Cloud
Currently (2011) bull 200 ontologiesbull 25 billion triplesbull 400m links httprichardcyganiakde200710lodimagemaphtml
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
111
Existing OntologiesThe existing ontologies in the Linked Data Cloud include ( httpwww4wiwissfu-berlindelodcloud )bull US census databull BBC music databasebull Gene ontologiesbull DBpedia general knowledge + YAGO + Cyc etcbull UK government databull geographical data in abundancebull national library catalogs (USA Germany etc)bull publications (DBLP)bull commercial productsbull all Pokemonsbull and many more
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
112
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
113
And the rest of the Web
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
114
RDFaRDFa is a W3C standard to annotate HTML pages with RDF data
ltdivgt
Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
115
RDFa
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
Namespace declaration (here a namespace provided by Google)
Everything inside this ltdivgt becomes a node of type vPerson
vPerson
rdftype
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
116
Naming a node
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt Martin Thunderbirdltbrgt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
We can also give the URI of the node
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
117
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan property=ldquovnamerdquogtMartin Thunderbirdltspangt Researcher in RockrsquoNrsquoRoll Music of 1935-1977ltbrgt 3764 Presley Boulevardltbrgt Memphis Tennesseeltdivgt
httpmartin
vPerson
rdftype
ldquoMartin Thunderbirdrdquo
vname
Statements are constructed with ldquoproperty=ldquo
Text becomes a string node in RDF
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
118
RDFa Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rel=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorelrdquo + ldquoresourcerdquo become a URI node in RDF
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
119
RDFa Inverse Statements
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo about=ldquohttpmartin-thunderbirdcommerdquogt ltspan rev=vfriendrdquo resource=ldquohttpbob-millerorgmerdquogt Bob Miller ltspangtltdivgt
httpmartin
vPerson
rdftype
httpbob-millerorgme vfriend
Links given by ldquorevrdquo become statements in the other direction
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
120
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt
ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquorelrdquo creates a link between the outer node and the inner node As before typeof
creates a new node
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
121
Inner Nodes
ltdiv xmlnsv=httprdfdata-vocabularyorg typeof=vPersonrdquo ltspan rel=vaddressrdquogt ltspan typeof=ldquovAddressrdquogt ltspan property=ldquovlocalityrdquogtMemphisltspangt ltspangt ltspangt ltdivgt
httpmartin
vPerson
rdftype
vaddress
vAddress
rdftype
ldquoMemphisrdquo
vlocality
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
122
RDFa Vocabulary
lttag xmlnsxxxx=httpgtlttaggt defines a namespacelttag typeof=classgt defines a new blank nodelttag about=urigt defines a new node with URIlttag property=predicategtvaluelttaggt defines a link of the outer node to a literallttag rel=predicate resource=uri gt defines a link of the outer node to a URIlttag rev=predicate resource=uri gt defines a link of the URI to the outer nodelttag rel=predicategt new node lttaggt defines a link of the outer node to the new node
which is isomorphic to an RDF graph
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
123
RDFa SummaryRDFa is a W3C standard to annotate HTML pages with RDF data
bull Grass root appeal(everybody can start annotating pages)
bull No data duplication(all data in one file)
bull Publisher independence (everybody can use his own attributes)
Advantages
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
124
RDFa ExampleExample with the Ubiquity RDFa parser on this page
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
RDF data following the Open Graph Protocol is often embedded in HTML pagesthus allowing the Facebook LIKE button to work
Facebook amp RDFa
125
ogp Open Graph Protocol httpogporgns
Beautiful mind IMDb
ogpsiteName
ogpMovie
Facebook has developed its own namespace
ogptype
wwwimdbcomtitlett0268978 lthtml xmlnsog=httpogpmens gt hellip ltmeta property=ogtype content=movie gt ltmeta property=fbapp_id content=lsquo123 gt helliplthtmlgt
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
Google amp RDFa
126
Google has defined its own namespace which allows annotating HTML pages with meta-information that will show up in ldquorich snippetsrdquo
Try it out
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
127
SigmaSigma is a Semantic Web search engine developed at the DERI Ireland It scraped RDFa and follows owlsameAs(httpsigma)
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
128
SigmaSigma also allows the user to correct factually wrong information (such as the urban legend that Elvis would be dead)
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
129
The Semantic WebThe Semantic Web provides standards tobull Identify entities (URIs)bull Express facts (RDF)bull Express concepts (RDFS)
bull Describe constraints (OWL)
bull Share vocabularies
bull Query knowledge (SPARQL)
bull Link data
bull Publish data (RDFa)
- The Semantic Web
- Organisation
- Motivation
- Motivation (2)
- Motivation (3)
- Motivation (4)
- Use cases
- Use cases (2)
- Merging
- The Semantic Web (2)
- The Semantic Web (3)
- The Semantic Web (4)
- The Semantic Web (5)
- URIs
- URIs (2)
- URIs and URLs
- Namespaces
- URI Use Cases
- URNs
- Example URNs
- Example URNs (2)
- UUIDs
- URIs Summary
- The Semantic Web (6)
- RDF
- RDF (2)
- RDF Graphs
- Sample RDF Graph
- Namespace Prefixes
- Default Prefix
- Tabular Data in RDF
- Tabular Data in RDF (2)
- Event Entities
- RDF Semantics
- Notation 3
- RDF XML Syntax
- RDF Concrete Syntax
- Labels
- The Semantic Web (7)
- Classes
- Classes in RDF
- Classes in RDF (2)
- Taxonomy
- Taxonomy (2)
- Taxonomy (3)
- SubclassOf Semantics
- RDFS Semantics
- The Semantic Web (8)
- Storing data
- Storing data (2)
- Cool URIs
- Cool URIs (2)
- Wersquore all one Graph
- Standard Vocabulary
- Standard Vocabulary (2)
- Dublin Core
- Creative Commons
- Sharing FOAF
- The Semantic Web (9)
- The Goal of OWL
- OWL Vocabulary
- OWL Undecidability
- OWL-DL Goal
- Intersection
- Union Intersection Negation
- Restrictions
- Restrictions (2)
- Restrictions (3)
- Subclass Assertions
- Type Assertions
- Fact Assertions
- Exercise
- Cardinality Restrictions
- Entity Set
- OWL-DL
- OWL-DL (2)
- OWL-DL (3)
- OWL-DL (4)
- OWL-DL (5)
- OWL-DL (6)
- OWL-DL (7)
- Reasoning Tasks
- Reasoning Tasks (2)
- Reasoning Tasks (3)
- OWL OWL-DL
- OWL-DL Summary
- The Semantic Web (10)
- SPARQL
- SPARQL Matching
- SPARQL Matching (2)
- SPARQL Result Sets
- SPARQL Endpoints
- SPARQL Example
- SPARQL Summary
- The Semantic Web (11)
- Linked Data Problem
- Linked Data Solution
- The Linking Data Project
- The Linked Data Cloud
- Existing Ontologies
- The Semantic Web (12)
- And the rest of the Web
- RDFa
- RDFa (2)
- Naming a node
- RDFa Statements
- RDFa Statements (2)
- RDFa Inverse Statements
- Inner Nodes
- Inner Nodes (2)
- RDFa Vocabulary
- RDFa Summary
- RDFa Example
- Facebook amp RDFa
- Google amp RDFa
- Sigma
- Sigma (2)
- The Semantic Web (13)
-
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