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Semantic Search with Semantic Web Presented by: Zahra Sadeghi 1
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Semantic Search with Semantic Web

Jan 22, 2017

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Page 1: Semantic Search with Semantic Web

Semantic Search with

Semantic Web

Presented by:

Zahra Sadeghi

1

Page 2: Semantic Search with Semantic Web

keyword-based search engines

• the quality of the search results:

– It often happens that relevant pages are not indexed by a traditional search engine

• very time-consuming task for the users who have to perform it manually.

– the result of a search engine is a single web page, and to retrieve information it is necessary to perform several queries.

• semantically similar queries can return different results

• very closely related to the spelling of the word and not to its meaning

• important information can be reached only if its specific internet address is known.

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The Original Web • 1989: Web was “invented” by Tim Berners-Lee

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Web of relationships amongst named objects

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Where we are Today

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What is the Problem?

• Consider a typical web page:

•The current Web represents information using: - natural language ( English,…) -graphics, multimedia •Humans can process this easily • can deduce facts from partial information

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• Semantic content is accessible to

humans but not (easily) to

computers…

Page 6: Semantic Search with Semantic Web

What information can we see… • WWW2002

• The eleventh international world wide web conference

• Sheraton waikiki hotel

• Honolulu, hawaii, USA

• 7-11 may 2002

• 1 location 5 days learn interact

• Registered participants coming from

• australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire

• Register now

• On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event …

• Speakers confirmed

• Tim berners-lee

• Tim is the well known inventor of the Web, …

• Ian Foster

• Ian is the pioneer of the Grid, the next generation internet …

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Page 7: Semantic Search with Semantic Web

What information can a machine

see… WWW2002

The eleventh inteqnational woqld wide web

confeqence

Sheqaton waikiki hotel

Honolulu, hawaii, USA

7-11 may 2002

1 location 5 days leaqn inteqact

Registeqed paqticipants coming fqom

austqalia, canada, chile denmaqk, fqance,

geqmany, ghana, hong kong, india,

iqeland, italy, japan, malta, new zealand,

the netheqlands, noqway, singapoqe,

switzeqland, the united kingdom, the united

states, vietnam, zaiqe

Registeq now

On the 7th May Honolulu will pqovide the

backdqop of the eleventh inteqnational woqld

wide web confeqence. This pqestigious event

Speakeqs confiqmed

Tim beqneqs-lee

Tim is the well known inventoq of the Web,

Ian Fosteq

Ian is the pioneeq of the Gqid, the next

geneqation inteqnet

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Page 8: Semantic Search with Semantic Web

The current Web =

the second Web generation

• The first generation Web started with handwritten HTML pages;

• The second generation made the step to machine generated and often active HTML pages.

• They were meant for direct human processing (reading, browsing, form-filling).

• The current web=syntactic web – A place where computers do the presentation (easy) and

people do the linking and interpreting (hard).

• The third generation Web= "Semantic Web", – aims at machine processable information.

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Why semantic web?

• The fact that accurate Natural Language Processing (NLP) is not yet achievable in general domains, has led to numerous efforts

– to create standardized semantic languages for the web.

• The semantic web aims

– to create content which both humans and machines can understand

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The main intent of the Semantic

Web

• to give machines much better access to information resources

• to improve the existing web with a semantic layer that allows machines to understand it

• to enable software programs to process information efficiently

• Moving from a Web of "finding things" to a Web of "doing things"

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solution=XML?

• HTML :

• a markup language for a specific kind of hypertext documents.

• Is not extensiable

• XML :

• a markup language for arbitrary document structure,

• Simplifies the process of defining and using metadata.

• Is a meta language: provides a basic structure and a set of rules for developing other languages.

• An XML document consists of a properly nested set of open and close tags, where each tag can have a number of attribute-value pairs.

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solution=XML?

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XML document = labelled tree

why not use XML to represent semantics?

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Solution:

XML markup with “meaningful” tags? <name>WWW2002 The eleventh inteqnational woqld wide webcon</name> <location>Sheqaton waikiki hotel Honolulu, hawaii, USA</location> <date>7-11 may 2002</date>

<slogan>1 location 5 days leaqn inteqact</slogan>

<participants>Registeqed paqticipants coming fqom austqalia, canada, chile denmaqk, fqance,

geqmany, ghana, hong kong, india, iqeland,

italy, japan, malta, new zealand, the

netheqlands, noqway, singapoqe, switzeqland,

the united kingdom, the united states,

vietnam, zaiqe</participants> <introduction>Registeq now On the 7

th May Honolulu will pqovide the

backdqop of the eleventh inteqnational woqld

wide web confeqence. This pqestigious event

Speakeqs confiqmed</introduction> <speaker>Tim beqneqs-lee</speaker>

<bio>Tim is the well known inventoq of the Web,</bio>…

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Still the Machine only sees…

<name>WWW2002

The eleventh inteqnational woqld wide webc</name>

<location>Sheqaton waikiki hotel

Honolulu, hawaii, USA</location>

<date>7-11 may 2002</date>

<slogan>1 location 5 days leaqn inteqact</slogan>

<paqticipants>Registeqed paqticipants coming fqom

austqalia, canada, chile denmaqk, fqance, g

eqmany, ghana, hong kong, india, iqeland,

italy, japan, malta, new zealand, the net

heqlands, noqway, singapoqe, switzeqland, the

united kingdom, the united states, vietnam,

zaiqe</paqticipants>

<intqoduction>Registeq now

On the 7th May Honolulu will pqovide the backdq

op of the eleventh inteqnational woqld wide w

eb confeqence. This pqestigious event

Speakeqs confiqmed</intqoduction>

<speakeq>Tim beqneqs-lee</speakeq>

<bio>Tim is the well known inventoq of the W</bio>

<speakeq>Ian Fosteq</speakeq>

<bio>Ian is the pioneeq of the Gqid, the ne</bio>

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Disadvantages of XML

• XML tags can add meaning to data

• Understanding the tags is only meaningful to humans.

• does not impose any common interpretation of the data contained in the document.

• XML is aiming at the structure of documents

• XML just describes grammars

•the vocabulary of the tags and their allowed combinations is not fixed

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"The author of the page is Ora".

<document href="page"> <author>Ora</author> </document>

<document> <details> <uri>href="page"</uri> <author> <name>Ora</name> </author> </details> </document>

<document> <author> <uri>href="page"</uri> <details> <name>Ora</name> </details> </author> </document>

<document href="http://www.w3.org/test/page" author="Ora" />

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The complexity of querying the

XML tree • the query you write has to be independent

of the choice of them.

• Must convert the set of all possible representations of a fact into one statement

• A standard ways of writing statements… ?

RDF The same RDF tree results from many XML trees.

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RDF

Resource Description Framework

• a language used for representing information about resources on the web.

• a basic ontology language.

• Motivation:

• to provide a standard for meta-data, for descriptions about resources on the web.

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The basic construction in RDF

• an object-attribute-value triple: • an object O has an attribute A with value V. • commonly written as A(O,V)

• A subject, predicate and object triple

• Resource, Property, and Property value triple • Resource = anything that can have a URI, such as

• "http://www.w3schools.com/RDF"

• Property = a Resource that has a name, such as • "author" or "homepage"

• Property value = the value of a Property, such as

• "Jan Egil " or "http://www.w3schools.com" • (note that a property value can be another resource)

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RDF Statements example • a Resource, a Property, and a Property value

= a subject, predicate and object

• "The author of http://www.w3schools.com/RDF is

Jan Egil Refsnes".

• The subject ? http://www.w3schools.com/RDF • The predicate? author • The object ? Jan Egil Refsnes

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RDF Syntax

• RDF has an XML syntax that has a specific meaning:

• Every Description element describes a resource

• Every attribute or nested element inside a Description is a property

of that Resource

• We can refer to resources by using URIs

<Description about="some.uri/person/ian_horrocks">

<hasColleague resource="some.uri/person/uli_sattler"/>

</Description>

<Description about="some.uri/person/uli_sattler">

<hasHomePage>http://www.cs.mam.ac.uk/~sattler</hasHomePage>

</Description>

<Description about="some.uri/person/carole_goble">

<hasColleague resource="some.uri/person/uli_sattler"/>

</Description>

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RDF Schema=RDFS • an object-oriented modelling language

• RDF :provides a model for describing information

• The semantics (meaning of the informations) is described using RDFS.

• RDF Schema „semantically extends‟ RDF to enable us

– to talk about classes of resources, and the properties that will be used with them.

– It allows you to define classes

– It allows you to define relationships between classes

– It allows you to define properties of classes

• RDFS = RDF Vocabulary Definition Language

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RDFS Example

• There is a relationship between Stream and BodyOfWater

• The relationship is called emptiesInto

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WATERSOURCE

Stream

River

Creek

BodyOfWater

Lake

sea

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<rdfs:Class rdf:ID="WaterSource" />

<rdfs:Class rdf:ID="Stream">

<rdfs:subClassOf rdf:resource="#WaterSource"/>

</rdfs:Class>

<rdfs:Class rdf:ID="BodyOfWater">

<rdfs:subClassOf rdf:resource="#WaterSource"/>

</rdfs:Class>

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<rdfs:Class rdf:ID="River">

<rdfs:subClassOf rdf:resource="#Stream"/>

</rdfs:Class>

<rdfs:Class rdf:ID="Lake">

<rdfs:subClassOf rdf:resource="#BodyOfWater"/>

</rdfs:Class>

...

<rdf:Property rdf:ID="emptiesInto">

<rdfs:range rdf:resource="# BodyOfWater"/>

<rdfs:domain rdf:resource="#River"/>

</rdf:Property>

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• Basically, we describe now real Web resources according to the

developed schema

• ...

• <River rdf:ID="Yangtze"

• <emptiesInto

• rdf:resource="EastChinaSea"/>

• </River>

• ...

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What are the advantages of

applying RDF Schema • Inference!

• We can infer new facts from already existing facts

• River is a subclass of Stream !

• Yangtze is a stream

• Stream is a subclass of WaterSource !

• Yangtze is a WaterSource

• River emptiesInto BodyOfWater !

• Yangtze (stream) empties Into EastChinaSea

• EastChinaSea is a BodyOfWater

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OWL

Web Ontology Language • Latest standard (February 2004) in ontology languages

• OWL is an ontology language

• primarily designed to describe and define classes.

• Classes are therefore the basic building blocks of an OWL ontology.

• Built on top of RDF (OWL semantically extends RDF(S)),

• OWL is for processing information on the web

• OWL was designed to be interpreted by computers

• OWL was not designed for being read by people

• OWL is written in XML

• OWL has three sublanguages

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Ontology

• Borrowed from philosophy : the study of “The nature of being”

• the exact description of things and their relationships. • Describes a list of terms and the relations between them • a "representation of a shared conceptualization of a

particular domain".

• have been developed in Artificial Intelligence to facilitate knowledge sharing and reuse.

• For the web: the exact description of web information and relationships between web information.

• in the context of the Semantic Web: is a document or file that formally defines the relations among terms

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An example

• Class_def Animal

class_def Plant

subclass_of Not Animal

class-def tree

subclass_of Plant

class_def branch

slot_constraint is-part_of

has_value tree

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the use of ontologies

• e-commerce sites – to enable machine-based communication

between buyer and seller, • in search engines.

– By using ontologies the search engines can escape from the current keyword-based approach,

– can find pages that contain syntactically different, but semantically similar words

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Agents

• They need to recognize, interpret, and respond to communication acts from other agents.

• They must communicate and understand meaning. • They must advertise their capabilities, and recognize the

capabilities of other agents. • They must locate meaningful information resources on

the Web and combine them

• suppose Agent 1 sends a message to Agent 2 and in this message is a pointer to Agent 1‟s ontology.

• Agent 2 can then look in Agent 1's ontology to see what the terms mean

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Semantic search

• Conventional Web expanded into a Semantic Web

• At the moment semantic search engines only exist for specialized areas of knowledge

• Shall use conceptual representation of Web pages

• Search engines in future should „understand‟ meaning of Web pages far enough to enable „sensible‟ queries

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An example

•An agent is searching for information about mechanical devices, as defined in a public ontology (SHO).

• A document contains the term “FUEL PUMP” which the agent has never encountered.

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• Swoogle : a system that automatically discovers SWDs(online documents written in RDF and OWL) using RDF and OWL.

• Developed by the university of Baltimore County

• human users are expected to be semantic web researchers

• Helps users integrate semantic web data distributed on the web.

• Facilates the finding of appropriate ontologies

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References

• The Semantic Web - on the respective Roles of XML and

RDF,Stefan Decker1, Frank van Harmelen3,4, Jeen

Broekstra4 Michael Erdmann5, Dieter Fensel3, Ian Horrocks

2, Michel Klein3, Sergey Melnik

• Semantic Web and RDF,Introduction,Denis Helic

• An Introduction to RDF(S) and a QuickTour of OWL,the

university of Manchester

• Where are the Semantics in the Semantic Web?, Michael

Uschold

• An Introduction to the Semantic Web, Considerations for

building multilingual Semantic Web sites and

applications,Jeremy J. Carroll

• Facilitating Semantic Web Search with Embedded Grammar

Tags,Gautham K.Dorai and Yaser Yacoob

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