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Ontology Languages

Ontology Languages. Sohn Jong-Soo Intelligent Information System lab. Department of Computer Science Korea University. Index. Ontology XML RDF OIL DAML OWL. 1. Ontology. Definition : Formal, explicit specification of a a shared conceptualization

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Ontology Languages

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  1. Ontology Languages Sohn Jong-Soo Intelligent Information System lab. Department of Computer Science Korea University

  2. Index • Ontology • XML • RDF • OIL • DAML • OWL

  3. 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

  4. 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

  5. 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

  6. DTD XML Style language Document Structure (Markup Language) Document Contents (instance) Style sheet 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)

  7. 2. XML (eXtensible Markup Language) • 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

  8. 2. XML (eXtensible Markup Language) • 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

  9. 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>

  10. 3. RDF (Resource Description Framework) • 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

  11. 3. RDF (Resource Description Framework) <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>mis026@korea.ac.kr</v:Email> </rdf:Description> </s:Creator> </rdf:Description> </rdf:RDF>

  12. 4. OIL (Ontology Inference Layer) • Satisfies the requirement of semantic web • Hierarchical layer structure for extension

  13. Description Logics: Formal Semantics& Reasoning Support Frame-based system: Epistemological Modeling Primitives OIL Web language: XML and RDF-based syntax 4. OIL (Ontology Inference Layer) • Based on Frame-based System, Description Logic and Web Languages

  14. 4. OIL (Ontology Inference Layer) • 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

  15. 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

  16. 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

  17. 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>

  18. 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)

  19. 6. OWL (Web Ontology Language) • 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

  20. 6. OWL (Web Ontology Language) 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>

  21. 7. Conclusion • 온톨로지를 표현하는 언어 • 많은 온톨로지 언어 중 중요하게 연구된 것을 위주로 조사 • 소개된 것 외에도 Ontolingua, SHOE, TopicMap등이 있음 • W3C의 표준화 추세 • W3C에서 표준으로 제정한 OWL이 가장 유력해 보임 • OWL에 대한 연구가 가장 활발 • OWL을 확장하여 표현력을 높이는 노력이 보임 • My impression • 비교적 예전의 언어를 이용하여 example을 만들기가 쉽지 않았음 • 시맨틱 웹 및 지능형 웹 서비스의 과거 및 현재를 돌아봄으로써 발전 방향에 대하여 다시한번 생각할 수 있는 계기 마련

  22. Thank you

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