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Ontology Languages

Explore the significance of ontology and XML languages in enabling web-based knowledge processing, sharing, and reuse. Ontology plays a crucial role in fostering a common understanding between humans and machines. XML, with its hierarchical structure and extensibility, facilitates large-scale electronic publishing and data exchange on the web. Learn about RDF as a markup language for representing distributed web resources. Discover the advantages and disadvantages of RDF in data representation and semantic understanding. Dive into OIL as an ontology inference layer that provides a hierarchical structure for semantic web requirements. Uncover the benefits and limitations of OIL in supporting Description Logics and formal reasoning. Explore how DAML combines XML and RDF for powerful semantic web representation and logic constraints.

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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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