Ontology Languages Semantic Web Lab

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




                    Ontology Languages

                     Sohn Jong-Soo

                     Intelligent Information System lab.
                     Department of Computer Science
                     Korea University

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




          Index
          1.       Ontology
          2.       XML
          3.       RDF
          4.       OIL
          5.       DAML
          6.       OWL

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




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




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




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




          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             XML           Style language



                   Document Structure   Document Contents
                                                             Style sheet
                   (Markup Language)        (instance)
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Dept. Computer Science, Korea Univ.                                         Intelligent Information System Lab.




          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




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




          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




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




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




          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



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




          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>



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




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




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




          4. OIL (Ontology Inference Layer)
           Based on Frame-based System, Description Logic and
            Web Languages



                        Description Logics:              Frame-based system:
                        Formal Semantics&               Epistemological Modeling
                        Reasoning Support                      Primitives




                                               OIL


                                           Web language:
                                      XML and RDF-based syntax
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Dept. Computer Science, Korea Univ.                                       Intelligent Information System Lab.




          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




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




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




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




          5. DAML (DARPA Agent Markup Language)

            <?xml version=”1.0”?>                                               <daml:Class rdf:ID=”Animal”>
            <rdf:RDF xmlns:rdf=”http://www.w3.org/1999/02/22/-rdf-syntzs-ns#”      <rdfs:label>Animal</rdfs:label>
               xmlns:rdfs=”http://www.w3.org/TR/1999/PR-rdf-schema-19990303#”   </daml:Class>
               xmlns:daml=”http://www.daml.org/2001/03/daml+oil#”
               xmlns = “http://www.daml.org/2001/03/daml+oil#”>
                                                                                <daml:Class rdf:ID=”girl-friend”>
                                                                                  <rdfs:subClassOf rdf:resource=”#Female”/>
            <daml:Ontology rdf:about=””>                                        </daml:Class>
            <daml:versionInfo>1.0</daml:versionInfo>
            <daml:import rdf:resource=”http://schema.org/base# “/>
            </daml:Ontology>                                                    <daml:Class rdf:ID=”Male”>
                                                                                  <rdfs:subClassOf rdf:resource=”#Animal”/>
                                                                                  <daml:disjointWith rdf:resource=”#Female”/>
            <daml:Class rdf:ID=”boy-friend”>                                    </daml:Class>
            <rdfs:subClassof rdf:resource=”#Male” />
            <rdfs:subClassOf>
               <daml:onProperty rdf:resource=”@has” />                          <daml:Class rdf:ID=”Female”>
               <daml:hasClass redf:resource=”#girl-friend” />                     <rdfs:subClassOf rdf:resource=”#Animal”/>
            </rdfs:subClassOf>                                                    <daml:disjointWith rdf:resource=”#Male”/>
            </daml:Class>                                                       </daml:Class>



                                                                                </rdf:RDF>




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




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




          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


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




          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>

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




          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 않
                   았음
                 ■ 시맨틱 웹 및 지능형 웹 서비스의 과거 및 현재를 돌아봄으로
                   써 발전 방향에 대하여 다시한번 생각할 수 있는 계기 마련


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




                                      Thank you



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