What is an Ontology? What is an Ontology? Catalog/ ID G eneral Logical constraints Term s/ glossary Thesauri “narrow er term ” relation Form al is-a Fram es (properties) Inform al is-a Form al instance V alue Restrs. D isjointness, Inverse, part- of…
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What is an Ontology?What is an Ontology?
Catalog/ID
GeneralLogical
constraints
Terms/glossary
Thesauri“narrower
term”relation
Formalis-a
Frames(properties)
Informalis-a
Formalinstance
Value Restrs.
Disjointness, Inverse, part-
of…
A Few Observations about OntologiesA Few Observations about Ontologies Simple ontologies can be built by non-experts
Ontologies can be semi-automatically generated from crawls of site such as yahoo!, amazon, excite, etc. Semi-structured sites can provide starting points
Ontologies are exploding (business pull instead of technology push) most e-commerce sites are using them - MySimon, Amazon,
Yahoo! Shopping, VerticalNet, etc. Controlled vocabularies (for the web) abound - SIC codes,
UMLS, UN/SPSC, Open Directory (DMOZ), Rosetta Net, SUO Business interest expanding – ontology directors, business
ontologies are becoming more complicated (roles, value restrictions, …), VC firms interested,
DTDs are making more ontology information available Markup Languages growing XML, RDF, DAML, RuleML, xxML “Real” ontologies are becoming more central to applications
Chimaera Chimaera –– A Ontology A Ontology Environment ToolEnvironment Tool
An interactive web-based tool aimed at supporting:•Ontology analysis (correctness, completeness, style, …)•Merging of ontological terms from varied sources•Maintaining ontologies over time•Validation of input
• Features: multiple I/O languages, loading and merging into multiple namespaces, collaborative distributed environment support, integrated browsing/editing environment, extensible diagnostic rule language
• Used in commercial and academic environments
• Available as a hosted service from www-ksl-svc.stanford.edu
• <daml:Class rdf:about="#Animal"> <rdfs:comment> Animals have exactly two parents, ie: If x is an animal, then it has exactly 2 parents (but it is NOT the case that anything that has 2 parents is an animal). </rdfs:comment> <rdfs:subClassOf> <daml:Restriction daml:cardinality="2"> <daml:onProperty rdf:resource="#hasParent"/> </daml:Restriction> </rdfs:subClassOf> </daml:Class> Such an assertion "
An even more compact idiom is to state that a whole set of classes are all pairwise disjoint. Rather than stating the individual disjointness relations, this can be stated for a set of classes in a single statement:
We can also identify a Class with the disjoint union of a set of other classes. In this case, we identify the Class Person with the disjoint union of the Classes Man and Woman.
<daml:Class rdf:about="#Person"> <rdfs:comment>every person is a man or a woman
We have already seen that we can construct a new class by taking the complementOf another class. In the same way, we can construct classes out of the intersection of other classes:<daml:Class rdf:ID="TallMan"> <daml:intersectionOf rdf:parseType="daml:collection"> <daml:Class rdf:about="#TallThing"/> <daml:Class rdf:about="#Man"/> </daml:intersectionOf> </daml:Class>
Notations for classes cont.4
Similarly, we can construct a class as the unionOf a set of classes:<daml:Class rdf:ID="MarriedPerson"> <daml:intersectionOf rdf:parseType="daml:collection"> <daml:Class rdf:about="#Person"/> <daml:Restriction daml:cardinality="1"> <daml:onProperty rdf:resource="#hasSpouse"/> </daml:Restriction> </daml:intersectionOf> </daml:Class>
Notations for classes cont.5
Just as for properties, a mechanism exists for declaring synonyms for classes:
<xsd:simpleType name="over59"> <!-- over59 is an XMLS datatype based on positiveIntege --> <!-- with the added restriction that values must be >= 59 --> <xsd:restriction base="xsd:positiveInteger"> <xsd:minInclusive
value="60"/> </xsd:restriction> </xsd:simpleType>Then we could reference elements of this file in DAML+OIL restrictions, <daml:Class rdf:ID="Senior"> <daml:intersectionOf rdf:parseType="daml:collection"> <daml:Class rdf:about="#Person"/> <daml:Restriction>
• We can also define individual objects in a class, e.g., Adam, a person of age 13 and shoesize 9.5:<Person rdf:ID="Adam"> <rdfs:label>Adam</rdfs:label> <rdfs:comment> Adam is a person.</rdfs:comment> <age><xsd:integer rdf:value="13"/></age><shoesize><xsd:decimal rdf:value="9.5"/></shoesize> </Person>
Defining individuals cont.1
A Person has a property called hasHeight, which is a Height. (hasHeight is a Property, or relation; Height is a Class, or kind of thing.)
Height is a Class described by an explicitly enumerated set. We can describe this set using the oneOf element. Like disjointUnionOf, oneOf uses the RDF-extending parsetype="daml:collection".
Defining individuals cont.3Finally, TallThing is exactly the class of things whose
hasHeight has the value tall: <daml:Class rdf:ID="TallThing"> <daml:sameClassAs> <daml:Restriction> <daml:onProperty rdf:resource="#hasHeight"/> <daml:hasValue rdf:resource="#tall"/> </daml:Restriction> </daml:sameClassAs> </daml:Class>
Defining individuals cont.4
• <daml:DatatypeProperty rdf:ID="shirtsize"> <rdfs:comment> shirtsize is a DatatypeProperty whose range is clothingsize. </rdfs:comment> <rdf:type rdf:resource="http://www.daml.org/2001/03/daml+oil#UniqueProperty"/> <rdfs:range rdf:resource="http://www.daml.org/2001/03/daml+oil-ex-dt#clothingsize"/> </daml:DatatypeProperty> <daml:DatatypeProperty rdf:ID="associatedData"> <rdfs:comment> associatedData is a DatatypeProperty without a range restriction. </rdfs:comment> </daml:DatatypeProperty>
Defining individuals cont.5
• <rdfs:Class rdf:ID="BigFoot"> <rdfs:comment> BigFoots (BigFeet?) are exactly those persons whose shosize is over12. </rdfs:comment> <daml:intersectionOf rdf:parseType="daml:collection"> <rdfs:Class rdf:about="#Person"/> <daml:Restriction> <daml:onProperty rdf:resource="#shoesize"/> <daml:hasClass rdf:resource="http://www.daml.org/2001/03/daml+oil-ex-dt#over12"/> </daml:Restriction> </daml:intersectionOf> </rdfs:Class>
Defining individuals cont.6
• <daml:Class rdf:about="#Person"> <rdfs:comment> Persons have at most 1 item of associatedData </rdfs:comment> <rdfs:subClassOf> <daml:Restriction> <daml:onProperty rdf:resource="#associatedData"/> <daml:maxCardinality>1</daml:maxCardinality> </daml:Restriction> </rdfs:subClassOf> </daml:Class>
Defining individuals cont.7
Now we can (try to) create several individuals. • <Person rdf:ID="Ian"> <shoesize>14</shoesize>