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ΑΝΑΠΑΡΑΣΤΑΣΗ ΓΝΩΣΗΣ ΣΤΟΝ ΠΑΓΚΟΣΜΙΟ ΙΣΤΟ

ΑΝΑΠΑΡΑΣΤΑΣΗ ΓΝΩΣΗΣ ΣΤΟΝ ΠΑΓΚΟΣΜΙΟ ΙΣΤΟ. OWL. Αναπαράσταση Γνώσης στον Παγκόσμιο Ιστό. http://aigroup.ceid.upatras.gr/index.php/el/krweb. RDF-RDFS Limitations. Binary ground predicates Only subclass & subproperty hierarchy Domain and range definitions. RDF doesn’t support….

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ΑΝΑΠΑΡΑΣΤΑΣΗ ΓΝΩΣΗΣ ΣΤΟΝ ΠΑΓΚΟΣΜΙΟ ΙΣΤΟ

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  1. ΑΝΑΠΑΡΑΣΤΑΣΗ ΓΝΩΣΗΣ ΣΤΟΝ ΠΑΓΚΟΣΜΙΟ ΙΣΤΟ OWL Αναπαράσταση Γνώσης στον Παγκόσμιο Ιστό http://aigroup.ceid.upatras.gr/index.php/el/krweb

  2. RDF-RDFS Limitations • Binary ground predicates • Only subclass & subproperty hierarchy • Domain and range definitions

  3. RDF doesn’t support… • Local scope of properties. • Disjointness of classes. • Boolean combinations of classes. • Cardinality restrictions. • Special characteristics of properties.

  4. OWL • OWL Full fully compatible with RDF • OWL DL efficient reasoning • OWL Lite easier to grasp/implement

  5. OWL Header <rdf:RDF xmlns:owl ="http://www.w3.org/2002/07/owl#" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:xsd ="http://www.w3.org/2001/XMLSchema#"> <owl:Ontology rdf:about=""> <rdfs:comment>An example OWL ontology</rdfs:comment> <owl:priorVersion rdf:resource="http://www.mydomain.org/uni-ns-old"/> <owl:imports rdf:resource="http://www.mydomain.org/persons"/> <rdfs:label>University Ontology</rdfs:label> </owl:Ontology>

  6. Class Element <owl:Class rdf:ID="associateProfessor"> <rdfs:subClassOf rdf:resource="#academicStaffMember"/> </owl:Class> Disjointness <owl:Class rdf:about="#associateProfessor"> <owl:disjointWith rdf:resource="#professor"/> <owl:disjointWith rdf:resource="#assistantProfessor"/> </owl:Class> Equivalence <owl:Class rdf:ID="faculty"> <owl:equivalentClass rdf:resource="#academicStaffMember"/> </owl:Class>

  7. Predefined Classes every class is a subclass of owl:Thing every class is a superclass of owl:Nothing

  8. Properties • Object properties, relates objects to other objects • Data type properties, relates objects to data type values <owl:DatatypeProperty rdf:ID="age"> <rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#nonNegativeInteger"/> </owl:DatatypeProperty> <owl:ObjectProperty rdf:ID="isTaughtBy"> <rdfs:domain rdf:resource="#course"/> <rdfs:range rdf:resource="#academicStaffMember"/> <rdfs:subPropertyOf rdf:resource="#involves"/> </owl:ObjectProperty>

  9. Inverse Properties <owl:ObjectProperty rdf:ID="teaches"> <rdfs:range rdf:resource="#course"/> <rdfs:domain rdf:resource="#academicStaffMember"/> <owl:inverseOf rdf:resource="#isTaughtBy"/> </owl:ObjectProperty> Equivalent Properties <owl:ObjectProperty rdf:ID="lecturesIn"> <owl:equivalentProperty rdf:resource="#teaches"/> </owl:ObjectProperty>

  10. Property Restrictions <owl:Classrdf:about="#firstYearCourse"> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#isTaughtBy"/> <owl:allValuesFromrdf:resource="#Professor"/> </owl:Restriction> </rdfs:subClassOf> </owl:Class> Every person that teaches a first Year Course is a professor (universal restriction) First-year courses are taught by professors only <owl:Classrdf:about="#mathCourse"> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#isTaughtBy"/> <owl:hasValuerdf:resource="#949318"/> </owl:Restriction> </rdfs:subClassOf> </owl:Class> Mathematics Courses are taught only by professor #949318

  11. Property Restrictions <owl:Classrdf:about="#academicStaffMember"> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#teaches"/> <owl:someValuesFromrdf:resource="#undergraduateCourse"/> </owl:Restriction> </rdfs:subClassOf> </owl:Class> For every academic Staff member there exists an undergraduate course that is taught by him (existential restriction) All academic staff members must teach at least one undergraduate course

  12. Cardinality Restriction <owl:Classrdf:about="#course"> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#isTaughtBy"/> <owl:minCardinalityrdf:datatype="&xsd;nonNegativeInteger"> 1 </owl:minCardinality> </owl:Restriction> </rdfs:subClassOf> </owl:Class> A course is taught by at least one Person

  13. Cardinality Restriction <owl:Classrdf:about="#department"> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#hasMember"/> <owl:minCardinalityrdf:datatype="&xsd;nonNegativeInteger"> 10 </owl:minCardinality> </owl:Restriction> </rdfs:subClassOf> <rdfs:subClassOf> <owl:Restriction> <owl:onPropertyrdf:resource="#hasMember"/> <owl:maxCardinalityrdf:datatype="&xsd;nonNegativeInteger"> 30 </owl:maxCardinality> </owl:Restriction> </rdfs:subClassOf> </owl:Class> A department must have at least 10 members but no more than 30.

  14. Special Properties • owl:TransitiveProperty “is taller than”, or “is ancestor of” • owl:SymmetricProperty “is sibling of”. • owl:FunctionalProperty a property that has at most one value for each object“has_mother” • owl:InverseFunctionalProperty a property for which two different objects cannot have the same value “has_IDnumber”

  15. Special Properties <owl:ObjectProperty rdf:ID="hasSameGradeAs"> <rdf:type rdf:resource="&owl;TransitiveProperty" /> <rdf:type rdf:resource="&owl;SymmetricProperty" /> <rdfs:domain rdf:resource="#student" /> <rdfs:range rdf:resource="#student" /> </owl:ObjectProperty>

  16. Boolean Combinations <owl:Class rdf:about="#course"> <rdfs:subClassOf> <owl:Class> <owl:complementOf rdf:resource="#staffMember"/> </owl:Class> </rdfs:subClassOf> </owl:Class> <owl:Class rdf:ID="peopleAtUni"> <owl:unionOf rdf:parseType="Collection"> <owl:Class rdf:about="#staffMember"/> <owl:Class rdf:about="#student"/> </owl:unionOf> </owl:Class>

  17. Boolean Combinations <owl:Class rdf:ID="facultyInCS"> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#faculty"/> <owl:Restriction> <owl:onProperty rdf:resource="#belongsTo"/> <owl:hasValue rdf:resource="#CSDepartment"/> </owl:Restriction> </owl:intersectionOf> </owl:Class>

  18. Boolean Combinations <owl:Classrdf:ID="adminStaff"> <owl:intersectionOfrdf:parseType="Collection"> <owl:Classrdf:about="#staffMember"/> <owl:Class> <owl:complementOf> <owl:Class> <owl:unionOfrdf:parseType="Collection"> <owl:Classrdf:about="#faculty"/> <owl:Classrdf:about="#techSupportStaff"/> </owl:unionOf> </owl:Class> </owl:complementOf> </owl:Class> </owl:intersectionOf> </owl:Class> administrative staff are those staff members that are neither faculty nor technical support staff

  19. Enumerations <owl:Class rdf:ID="weekdays"> <owl:oneOf rdf:parseType="Collection"> <owl:Thing rdf:about="#Monday"/> <owl:Thing rdf:about="#Tuesday"/> <owl:Thing rdf:about="#Wednesday"/> <owl:Thing rdf:about="#Thursday"/> <owl:Thing rdf:about="#Friday"/> <owl:Thing rdf:about="#Saturday"/> <owl:Thing rdf:about="#Sunday"/> </owl:oneOf> </owl:Class>

  20. Instances (RDF) <rdf:Description rdf:ID="949352"> <rdf:type rdf:resource="#academicStaffMember"/> </rdf:Description> or <academicStaffMember rdf:ID="949352"/> We can also provide further details, such as: <academicStaffMember rdf:ID="949352"> <uni:age rdf:datatype="&xsd;integer">39</uni:age> </academicStaffMember>

  21. Instances (RDF) Just because two instances have a different name or ID does not imply that they are different individuals. To ensure that different individuals are indeed recognized as such, we must explicitly assert their inequality: <lecturer rdf:ID="949318"> <owl:differentFrom rdf:resource="#949352"/> </lecturer> to state the inequality of a large number of individuals: <owl:AllDifferent> <owl:distinctMembers rdf:parseType="Collection"> <lecturer rdf:about="#949318"/> <lecturer rdf:about="#949352"/> <lecturer rdf:about="#949111"/> </owl:distinctMembers> </owl:AllDifferent>

  22. Layering of OWL • OWL Full • OWL DL • Vocabulary partitioning. • Explicit typing. • Property separation. • No transitive cardinality restrictions. • Restricted anonymous classes. • OWL Lite • The constructors owl:oneOf, owl:disjointWith, owl:unionOf, owl:complementOf, and owl:hasValue are not allowed. • Cardinality statements can only be made on the values 0 or 1 and no longer on arbitrary non-negative integers. • owl:equivalentClass statements can no longer be made between anonymous classes but only between class identifiers.

  23. open-world assumption • we may not deduce falsity from the absence of truth • non-unique-name assumption • Just because two instances have a different name or ID does not imply that they are different individuals

  24. Παραδείγματα από travel.owl <owl:Classrdf:ID="Sunbathing"> <rdfs:subClassOf> <owl:Classrdf:about="#Relaxation"/> </rdfs:subClassOf> </owl:Class> <owl:Classrdf:ID="QuietDestination"> <owl:equivalentClass> <owl:Class> <owl:intersectionOfrdf:parseType="Collection"> <owl:Classrdf:ID="Destination"/> <owl:Class> <owl:complementOf> <owl:Classrdf:about="#FamilyDestination"/> </owl:complementOf> </owl:Class> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> <rdfs:commentrdf:datatype="http://www.w3.org/2001/XMLSchema#string"> A destination that is not frequented by noisy families. </rdfs:comment> </owl:Class>

  25. Παραδείγματα από travel.owl <owl:Class rdf:ID="BackpackersDestination“> <owl:equivalentClass> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Destination"/> <owl:Restriction> <owl:onProperty> <owl:ObjectProperty rdf:about="#hasAccommodation"/> </owl:onProperty> <owl:someValuesFrom> <owl:Class rdf:about="#BudgetAccommodation"/> </owl:someValuesFrom> </owl:Restriction> <owl:Restriction> <owl:someValuesFrom> <owl:Class> <owl:unionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Sports"/> <owl:Class rdf:about="#Adventure"/> </owl:unionOf> </owl:Class> </owl:someValuesFrom> <owl:onProperty> <owl:ObjectProperty rdf:about="#hasActivity"/> </owl:onProperty> </owl:Restriction> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> <rdfs:comment rdf:datatype="http://www.w3.org/2001/XMLSchema#string"> A destination that provides budget accommodation and offers sport or adventure activities. </rdfs:comment> </owl:Class>

  26. Παραδείγματα από african.owl <owl:Class rdf:about="#carnivore"> <owl:equivalentClass> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Restriction> <owl:onProperty> <owl:TransitiveProperty rdf:about="#is-part-of"/> </owl:onProperty> <owl:someValuesFrom> <owl:Class rdf:about="#animal"/> </owl:someValuesFrom> </owl:Restriction> <owl:Class rdf:about="#animal"/> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> </owl:Class> <owl:Class rdf:ID="herbivore"> <owl:equivalentClass> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:ID="animal"/> <owl:Restriction> <owl:someValuesFrom> <owl:Class> <owl:unionOf rdf:parseType="Collection"> <owl:Class rdf:ID="plant"/> <owl:Restriction> <owl:allValuesFrom> <owl:Class rdf:about="#plant"/> </owl:allValuesFrom> <owl:onProperty> <owl:TransitiveProperty rdf:ID="is-part-of"/> </owl:onProperty> </owl:Restriction> </owl:unionOf> </owl:Class> </owl:someValuesFrom> <owl:onProperty> <owl:ObjectProperty rdf:ID="eats"/> </owl:onProperty> </owl:Restriction> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> </owl:Class> <owl:Class rdf:ID="lion"> <rdfs:subClassOf> <owl:Class rdf:ID="carnivore"/> </rdfs:subClassOf> <rdfs:subClassOf> <owl:Restriction> <owl:allValuesFrom rdf:resource="#herbivore"/> <owl:onProperty> <owl:ObjectProperty rdf:about="#eats"/> </owl:onProperty> </owl:Restriction> </rdfs:subClassOf> </owl:Class>

  27. Παραδείγματα από african.owl <owl:ObjectProperty rdf:about="#eats"> <owl:inverseOf> <owl:ObjectProperty rdf:about="#eaten-by"/> </owl:inverseOf> <rdfs:domain rdf:resource="#animal"/> </owl:ObjectProperty> <owl:ObjectProperty rdf:about="#eaten-by"> <owl:inverseOf rdf:resource="#eats"/> <rdfs:range rdf:resource="#animal"/> </owl:ObjectProperty> <owl:TransitiveProperty rdf:about="#is-part-of"> <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#ObjectProperty"/> </owl:TransitiveProperty>

  28. Παραδείγματα από generations.owl <owl:Class rdf:ID="GrandFather"> <owl:equivalentClass> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Person"/> <owl:Restriction> <owl:onProperty> <owl:ObjectProperty rdf:about="#hasChild"/> </owl:onProperty> <owl:someValuesFrom> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Person"/> <owl:Restriction> <owl:someValuesFrom rdf:resource="#Person"/> <owl:onProperty> <owl:ObjectProperty rdf:about="#hasChild"/> </owl:onProperty> </owl:Restriction> </owl:intersectionOf> </owl:Class> </owl:someValuesFrom> </owl:Restriction> <owl:Restriction> <owl:onProperty> <owl:FunctionalProperty rdf:ID="hasSex"/> </owl:onProperty> <owl:hasValue> <Sex rdf:ID="MaleSex"/> </owl:hasValue> </owl:Restriction> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> </owl:Class> <owl:Class rdf:ID="Sibling"> <owl:equivalentClass> <owl:Class> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Person"/> <owl:Restriction> <owl:someValuesFrom rdf:resource="#Person"/> <owl:onProperty> <owl:SymmetricProperty rdf:about="#hasSibling"/> </owl:onProperty> </owl:Restriction> </owl:intersectionOf> </owl:Class> </owl:equivalentClass> </owl:Class>

  29. Protégé-OWL • The Protégé-OWL editor enables users to: • Load and save OWL and RDF ontologies. • Edit and visualize classes, properties, and SWRL rules. • Define logical class characteristics as OWL expressions. • Execute reasoners such as description logic classifiers. • Edit OWL individuals for Semantic Web markup.

  30. SWRL Semantic Web Rule Language (SWRL) is an expressive OWL-based rule language. SWRL allows users to write rules that can be expressed in terms of OWL concepts to provide more powerful deductive reasoning capabilities than OWL alone. Example:A person with a male sibling has a brother. Person(?p) ^ hasSibling(?p,?s) ^ Man(?s) -> hasBrother(?p,?s) http://protege.cim3.net/cgi-bin/wiki.pl?SWRLTab http://protege.cim3.net/cgi-bin/wiki.pl?SWRLLanguageFAQ

  31. Jena-OWL API • The Jena Framework includes: • an API for reading, processing and writing RDF data in XML, N-triples and Turtle formats; • an ontology API for handling OWL and RDFS ontologies; • a rule-based inference engine for reasoning with RDF and OWL data sources; • stores to allow large numbers of RDF triples to be efficiently stored on disk; • a query engine compliant with the latest SPARQL specification • servers to allow RDF data to be published to other applications using a variety of protocols, including SPARQ

  32. Jena-OWL API • Δημιουργία OWL μοντέλου OntModel m = ModelFactory.createOntologyModel( OntModelSpec.OWL_DL_MEM_RULE_INF); http://jena.apache.org/documentation/ontology/index.html

  33. Other Java APIs • Protégé-OWL API • http://protegewiki.stanford.edu/wiki/ProtegeOWL_API_Programmers_Guide • OWL API • http://owlapi.sourceforge.net/

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