ontology languages

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Dept. Computer Science, Korea Univ.Dept. Computer Science, Korea Univ. Intelligent Information System Lab.Intelligent Information System Lab.

Sohn Jong-Soo

Intelligent Information System lab.Department of Computer ScienceKorea University

Ontology Languages

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Index

1. Ontology2. XML3. RDF4. OIL5. DAML6. OWL

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1. Ontology

Definition : Formal, explicit specification of a a shared conceptualization

Ontology can be used and shared by agents

Ontology languages■ To be understood by humans intuitively■ Capturing of meaning (semantics) of data■ Inference mechanism with completeness,

preciseness and efficiency■ Interoperability and compatibility

Combined with web languages s.a. XML and RDF

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1. Ontology

Crucial role in enabling web-based knowledge processing, sharing and reuse■ Human-beings and machines communicate each

other common understanding of topics between people and

applications

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1. Ontology

Conceptual structures for machine processible data on the web■ Formal tools to structure semantic data■ Formal conceptualizations of particular domains

Metadata schema with controlled vocabulary of concepts■ Semantic metadata for web pages■ RDF & RDFS as metadata formats

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2. XML (eXtensible Markup Language)

Standard markup language to represent the user-defined markup language

meta markup language■ Markup language to define another markup language

Simple, but flexible text-format defined from SGML

Large-scale electronic publishing to meet the role in the exchange of wide variety of data on the web and elsewhere

Hierarchical structure with tag (DTD)DTD

Document Structure(Markup Language)

XML

Document Contents (instance)

Style sheet

Style language

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XML related standards■ DTD (Document Type Definition)

Defines the logic structure of XML documents Defines contents & attributes of each component Defines objects

■ XSL (eXtensible Style Sheet) Defines the style to each component of XML documents Documents transformation

■ CSS (Cascading Style Sheet) Some functionality as XSL Limitation in the style definition

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Advantages■ Data representation ■ structured & independent■ Data sharing and interoperability■ Hierarchical, composite data

Disadvantages■ Lack of representation of relationship between

objects■ Lack of representation of data meaning■ Lack of inheritance of meaning

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3. RDF (Resource Description Framework)

Markup language based on XML syntax Developed to representation the multiple,

various resources dispersed in the distributed web environment

Used as a basis for the other markup language Data representation : triple representation as

follow <object, property, value>

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Advantages■ Representation of data with the meaning■ Environment in which computer can understand and

process the data■ Flexible capability to representation the meta data■ Mean of information exchange in heterogeneous

distributed environment■ Description of constants by the semantic network

Disadvantages■ Lack of affection inference mechanism■ Weak in the representation of semantic of data

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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:s="http://iis.korea.ac.kr/schema/">

<rdf:Description about="http://iis.korea.ac.kr/Home/Sohn"><s:Creator> <rdf:Description about="http://iis.korea.ac.kr/stdId/2005020626">

<rdf:type resource="http://iis.korea.ac.kr/schema/Person"/><v:Name>Sohn JongSoo</v:Name><v:Email>[email protected]</v:Email>

</rdf:Description></s:Creator>

</rdf:Description></rdf:RDF>

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4. OIL (Ontology Inference Layer)

Satisfies the requirement of semantic web Hierarchical layer structure for extension

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Based on Frame-based System, Description Logic and Web Languages

OIL

Frame-based system:Epistemological Modeling

Primitives

Description Logics:Formal Semantics&Reasoning Support

Web language:XML and RDF-based syntax

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Advantages■ Hierarchical extensions■ Effective inference mechanism based on the

Description Logic■ Well-defined semantics

Disadvantages■ Impossible to define the default-value■ Impossible to provide the meta-class■ Impossible to support the concrete domain

Limitation in the OIL extension and ontology transformation

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5. DAML (DARPA Agent Markup Language) Based on XML and RDF

Combines the advantage of various, multiple semantic web languages■ Combination of DAML + OIL■ DAML-S

Automatic Web Service retrieval and execution

■ DAML-L Logic representation

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5. DAML (DARPA Agent Markup Language) Advantages

■ Powerful in the representation of meaning and constraints

■ Support for the XML-Schema data type■ Support well-defined semantics■ Support default value

Disadvantages■ Can’t exclude the RDF and XML■ Can’t be formal language■ Less extensible compared with OIL

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5. DAML (DARPA Agent Markup Language)

<?xml version=”1.0”?> <rdf:RDF xmlns:rdf=”http://www.w3.org/1999/02/22/-rdf-syntzs-ns#” xmlns:rdfs=”http://www.w3.org/TR/1999/PR-rdf-schema-19990303#” xmlns:daml=”http://www.daml.org/2001/03/daml+oil#” xmlns = “http://www.daml.org/2001/03/daml+oil#”>

<daml:Ontology rdf:about=””> <daml:versionInfo>1.0</daml:versionInfo> <daml:import rdf:resource=”http://schema.org/base# “/> </daml:Ontology>

<daml:Class rdf:ID=”boy-friend”> <rdfs:subClassof rdf:resource=”#Male” /> <rdfs:subClassOf> <daml:onProperty rdf:resource=”@has” /> <daml:hasClass redf:resource=”#girl-friend” /> </rdfs:subClassOf> </daml:Class>

<daml:Class rdf:ID=”Animal”> <rdfs:label>Animal</rdfs:label> </daml:Class>

<daml:Class rdf:ID=”girl-friend”> <rdfs:subClassOf rdf:resource=”#Female”/> </daml:Class>

<daml:Class rdf:ID=”Male”> <rdfs:subClassOf rdf:resource=”#Animal”/> <daml:disjointWith rdf:resource=”#Female”/> </daml:Class>

<daml:Class rdf:ID=”Female”> <rdfs:subClassOf rdf:resource=”#Animal”/> <daml:disjointWith rdf:resource=”#Male”/> </daml:Class>

</rdf:RDF>

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6. OWL (Web Ontology Language)

Three species of OWL■ OWL full is union of OWL syntax and RDF■ OWL DL restricted to FOL fragment (¼ DAML+OIL)■ OWL Lite is “easier to implement” subset of OWL DL

Semantic layering■ DL semantics officially definitive

OWL DL based on SHIQ Description Logic■ In fact it is equivalent to SHOIN(Dn) DL

OWL DL Benefits from many years of DL research■ Well defined semantics■ Formal properties well understood (complexity,

decidability)■ Known reasoning algorithms■ Implemented systems (highly optimised)

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Relationships between classes■ equivalentClass■ subClassOf■ Intersection, union, complement, disjunction

Relationships between instances■ sameAs, differentFrom

Properties of properties■ Domain, Range■ Cardinality■ Transitive, Symmetric■ allValuesFrom, someValuesFrom■ Functional, InverseFunctional

Relationships between properties■ subPropertyOf■ inverseOf

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RDFS syntax

<owl:Class> <owl:intersectionOf rdf:parseType=" collection"> <owl:Class rdf:about="#Person"/> <owl:Restriction> <owl:onProperty rdf:resource="#hasChild"/> <owl:toClass> <owl:unionOf rdf:parseType=" collection"> <owl:Class rdf:about="#Doctor"/> <owl:Restriction> <owl:onProperty rdf:resource="#hasChild"/> <owl:hasClass rdf:resource="#Doctor"/> </owl:Restriction> </owl:unionOf> </owl:toClass> </owl:Restriction> </owl:intersectionOf></owl:Class>

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7. Conclusion

온톨로지를 표현하는 언어■ 많은 온톨로지 언어 중 중요하게 연구된 것을 위주로 조사■ 소개된 것 외에도 Ontolingua, SHOE, TopicMap 등이 있음

W3C 의 표준화 추세■ W3C 에서 표준으로 제정한 OWL 이 가장 유력해 보임■ OWL 에 대한 연구가 가장 활발■ OWL 을 확장하여 표현력을 높이는 노력이 보임

My impression■ 비교적 예전의 언어를 이용하여 example 을 만들기가 쉽지

않았음■ 시맨틱 웹 및 지능형 웹 서비스의 과거 및 현재를

돌아봄으로써 발전 방향에 대하여 다시한번 생각할 수 있는 계기 마련

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Thank you