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The Semantic                             Web – Part 2Semantic CMS Community Lecturer Organization                         ...
Page:                           Part I: Foundations(1)   Introduction of Content                   Foundations of Semantic...
Page: 3       Semantic Web Layer CakeA language for queryinginformation specified in         RDF.  A model for describingr...
Page: 4   RDF RDF   can be used to make statements about single  resources identified by URIs RDF is able to define rela...
Page: 5    RDF Classes                                  http://example.org/rel/Brand   http://example.org/myCar           ...
Page: 6       RDF Properties   http://example.org/my      http://example.org/rel/Brand   http://example.org/University    ...
Page: 7www.iks-project.eu             Copyright IKS Consortium
Page: 8  RDF Schema “RDFsvocabulary description language, RDF Schema, is a semantic extension of RDF. It provides mechani...
Page: 9  RDF Schema RDFS  does not provide a specific vocabulary for describing properties such as “Brand”, but a languag...
Page: 10  RDFS Classes “Resources may be divided into groups called classes. The members of a class are known as instance...
Page: 11  RDFS Classes Thepredicate rdf:type assigns the object as type of the subject Theassignment to a type is not ex...
Page: 12  RDFS Classes A resource can be defined as a class explicitly The type rdfs:Class defines a resource as a class...
Page: 13  Hierarchies of Classes “Theproperty rdfs:subClassOf is an instance of rdf:Property that is used to state that a...
Page: 14RDFS Constructs - Predefined Classes                               All things described by RDF are called resource...
Page: 15  RDFS Properties “TheRDF Concepts and Abstract Syntax specification describes the concept of an RDF property as ...
Page: 16  Hierarchies of Properties “The property rdfs:subPropertyOf is an instance of rdf:Property that is used to state...
Page: 17       Property Restrictions  http://example.org/my      http://example.org/rel/Brand    http://example.org/Univer...
Page: 18   Domain “rdfs:domain   is an instance of rdf:Property that is  used to state that any resource that has a given...
Page: 19  Range “rdfs:range   is an instance of rdf:Property that is used  to state that the values of a property are ins...
Page: 20    RDFS Constructs – Predefined    Properties (I)                            rdfs:range is an instance of rdf:Pro...
Page: 21      RDFS Constructs – Predefined      Properties (II)                              rdfs:label is an instance of ...
Page: 22          RDFS - Example                                                                                          ...
Page: 23       Back to the Cake ...A language for queryinginformation specified in                                        ...
Page: 24  Why is RDFS not enough? RDFS     cannot express negations Defined      property restrictions are global Missi...
Page: 25  OWL – Web Ontology  Language “The OWL Web Ontology Language is designed for use  by applications that need to p...
Page: 26  OWL – The Story 2004 - OWL W3C Recommendation 2009 - OWL 2 W3C RecommendationOWL = Web Ontology Language Why ...
Page: 27    Dialects of OWL OWL         Lite       Provides classification hierarchy and simple constraint        featur...
Page: 28  How does OWL look like?  RDF Document Basic structure            of an OWL Document                   Namespace...
Page: 29  Simple OWL Classes Comparable    to RDFS classes Every individual in OWL is a member of the class  owl:Thing ...
Page: 30  Hierarchies of Classes Thedefinition of basic taxonomies for classes can be done by rdfs:subClassOf. rdfs:subC...
Page: 31  Disjoint Classes “The disjointness of a set of classes can be expressed using the owl:disjointWith constructor....
Page: 32   Infer about Disjoint Classes                                                   The class “Car” is a  <owl:Class...
Page: 33      Individuals   In addition to the definition of classes, we also need to     describe the members of classes...
Page: 34  Simple Properties “This world of classes and individuals would be pretty  uninteresting if we could only define...
Page: 35  Object Properties Objectproperties relate instances of classes by rdfs:domain and rdfs:range.                  ...
Page: 36  Datatype Properties Datatypeproperties relate class instances and data values using rdfs:domain and rdfs:range....
Page: 37   Recommended XML Schema   datatypesxsd:string                  xsd:normalizedString          xsd:booleanxsd:deci...
Page: 38  Cardinality Constraints for  Properties owl:minCardinality   defines the minimal cardinality for  the value of ...
Page: 39  Cardinality Constraints for  Properties “owl:cardinality                 permits the specification of exactly t...
Page: 40  Property Restrictions “The owl:allValuesFrom restriction requires that for  every instance of the class that ha...
Page: 41  Property Restrictions                                     Restriction on property    <owl:Class rdf:ID=“Car">   ...
Page: 42  Property Restrictions with  Constants “owl:hasValue   allows us to specify classes based on the existence of pa...
Page: 43  Intersection owl:intersectionOf         defines a class as an intersection of other classes.<owl:Class rdf:ID=“...
Page: 44  Union “owl:unionOf    describes a class that contains those individuals that occur in at least one of the class...
Page: 45  Complement “The owl:complementOf construct selects all individuals from the domain of discourse that do not bel...
Page: 46   If you want to know more ... There  is stuff about OWL out there, which is not part of  this course:      Cla...
Page: 47  OWL 2 OWL   2 adds new functionality to OWL, while the overall  structure is very similar OWL 2 provides synta...
Page: 48       Back to the Cake ...                                                                     Highly expressive ...
Page: 49  Lessons Learned Now    you should know ...    ... what is the main difference between RDF and ontology     lan...
Page: 50 References and Additional Material RDFVocabulary Description Language 1.0: RDF Schema    http://www.w3.org/TR/r...
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Lecture the semantic_web_part_2

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Lecture the semantic_web_part_2

  1. 1. The Semantic Web – Part 2Semantic CMS Community Lecturer Organization Modeling Complex Knowledge Date of presentation Domains Co-funded by the 1 Copyright IKS Consortium European Union
  2. 2. Page: Part I: Foundations(1) Introduction of Content Foundations of Semantic (2) Management Web Technologies Part II: Semantic Content Part III: Methodologies Management Knowledge Interaction Requirements Engineering(3) (7) and Presentation for Semantic CMS(4) Knowledge Representation and Reasoning (8) Designing Semantic CMS Semantifying(5) Semantic Lifting (9) your CMS Storing and Accessing Designing Interactive(6) Semantic Data (10) Ubiquitous ISwww.iks-project.eu Copyright IKS Consortium
  3. 3. Page: 3 Semantic Web Layer CakeA language for queryinginformation specified in RDF. A model for describingresources with properties A format for specifying structured and property values. data in a machine-readable form Unique identification of resources Semantic Web Layer Cake, Image source: http://www.w3.org/2007/03/layerCake.svg www.iks-project.eu Copyright IKS Consortium
  4. 4. Page: 4 RDF RDF can be used to make statements about single resources identified by URIs RDF is able to define relations among resources Literals can be assigned as values to properties of resources http://example.org/rel/Brand http://example.org/myCar http://example.org/Jaguar http://example.org/rel/Model http://example.org/myCar XF www.iks-project.eu Copyright IKS Consortium
  5. 5. Page: 5 RDF Classes http://example.org/rel/Brand http://example.org/myCar http://example.org/Jaguar Car Vehicle http://example.org/VWHow are these terms related Do these terms have to each other? anything in common? www.iks-project.eu Copyright IKS Consortium
  6. 6. Page: 6 RDF Properties http://example.org/my http://example.org/rel/Brand http://example.org/University Car Paderborn Is “UniversityPaderborn” a valid value for property “Brand”? We need to do statements about properties  What is the type of the property? Definition of valid types for subjects and objects Definition of hierarchies of properties www.iks-project.eu Copyright IKS Consortium
  7. 7. Page: 7www.iks-project.eu Copyright IKS Consortium
  8. 8. Page: 8 RDF Schema “RDFsvocabulary description language, RDF Schema, is a semantic extension of RDF. It provides mechanisms for describing groups of related resources and the relationships between these resources.” W3C Recommendation  RDF Vocabulary Description Language 1.0: RDF Schema The RDFS namespace is: “rdfs: http://www.w3.org/2000/01/rdf-schema#”  But RDFS also uses elements from the rdf namespace! http://www.w3.org/TR/rdf-schema/ www.iks-project.eu Copyright IKS Consortium
  9. 9. Page: 9 RDF Schema RDFS does not provide a specific vocabulary for describing properties such as “Brand”, but a language to define vocabularies RDFS uses RDF to define RDF vocabularies Due to its limited expressiveness, RDFS is a language to define lightweight ontologies http://www.w3.org/TR/rdf-schema/ www.iks-project.eu Copyright IKS Consortium
  10. 10. Page: 10 RDFS Classes “Resources may be divided into groups called classes. The members of a class are known as instances of the class. Classes are themselves resources.” Themembers (resources) of a class A are termed instances of the class A Classes are resource, e.g. “http://example.org/CarManufacturer” and can be described by RDF properties www.iks-project.eu Copyright IKS Consortium
  11. 11. Page: 11 RDFS Classes Thepredicate rdf:type assigns the object as type of the subject Theassignment to a type is not exclusive  A subject can be typed by several objects! Example: ex:Jaguar rdf:type ex:CarManufacturer www.iks-project.eu Copyright IKS Consortium
  12. 12. Page: 12 RDFS Classes A resource can be defined as a class explicitly The type rdfs:Class defines a resource as a class Example: ex:CarManufacturer rdf:type rdfs:Class rdfs:Class is the “class of all classes”, i.e.: rdfs:Class rdf:type rdfs:Class www.iks-project.eu Copyright IKS Consortium
  13. 13. Page: 13 Hierarchies of Classes “Theproperty rdfs:subClassOf is an instance of rdf:Property that is used to state that all the instances of one class are instances of another.” The subject and object of the predicate “rdfs:subClassOf” must be instances of rdfs:Class The property rdfs:subClassOf is transitive Example: ex:CarManufacturer rdfs:subClassOf ex:Company www.iks-project.eu Copyright IKS Consortium
  14. 14. Page: 14RDFS Constructs - Predefined Classes All things described by RDF are called resources, andrdfs:Resource are instances of the class rdfs:Resource. This is the class of resources that are classes.rdfs:Class rdfs:Class is an instance of rdfs:Class. The class rdfs:Literal is the class of literal values suchrdfs:Literal as strings and integers. rdfs:Literal is an instance of rdfs:Class. rdfs:Literal is a subclass of rdfs:Resource. rdfs:Datatype is the class of datatypes. rdfs:Datatype isrdfs:Datatype both an instance of and a subclass of rdfs:Class. Each instance of rdfs:Datatype is a subclass of rdfs:Literal. The class rdf:XMLLiteral is the class of XML literalrdf:XMLLiteral values. rdf:XMLLiteral is an instance of rdfs:Datatype and a subclass of rdfs:Literal. Typos? rdf:Property is the class of RDF properties. rdf:Propertyrdf:Property is an instance of rdfs:Class. http://www.w3.org/TR/rdf-schema/ www.iks-project.eu Copyright IKS Consortium
  15. 15. Page: 15 RDFS Properties “TheRDF Concepts and Abstract Syntax specification describes the concept of an RDF property as a relation between subject resources and object resources” A resource can be defined as property explicitly ex:Brand rdf:type rdf:Property www.iks-project.eu Copyright IKS Consortium
  16. 16. Page: 16 Hierarchies of Properties “The property rdfs:subPropertyOf is an instance of rdf:Property that is used to state that all resources related by one property are also related by another.” The subject and object of the predicate “rdfs:subPropertyOf ” must be instances of rdf:Property The property rdfs:subPropertyOf is transitive Example: ex:friendOf rdfs:subPropertyOf ex:knows www.iks-project.eu Copyright IKS Consortium
  17. 17. Page: 17 Property Restrictions http://example.org/my http://example.org/rel/Brand http://example.org/University Car Paderborn Is “UniversityPaderborn” a valid value for property “Brand”? Weneed to express, that only subjects and objects of specific types should be used for the predicate “Brand” www.iks-project.eu Copyright IKS Consortium
  18. 18. Page: 18 Domain “rdfs:domain is an instance of rdf:Property that is used to state that any resource that has a given property is an instance of one or more classes.” States that each subject with the predicate (property) is an instance of the defined class Ifmore than one domain is defined, the subjects are instances of all classes! Example: ex:Brand rdfs:domain ex:Vehicle www.iks-project.eu Copyright IKS Consortium
  19. 19. Page: 19 Range “rdfs:range is an instance of rdf:Property that is used to state that the values of a property are instances of one or more classes.” States that each object of the predicate (property) is an instance of the defined class If more than one range is defined, the objects are instances of all classes! Example: ex:Brand rdfs:range ex:Company www.iks-project.eu Copyright IKS Consortium
  20. 20. Page: 20 RDFS Constructs – Predefined Properties (I) rdfs:range is an instance of rdf:Property that is used tordfs:range state that the values of a property are instances of one or more classes. rdfs:domain is an instance of rdf:Property that is usedrdfs:domain to state that any resource that has a given property is an instance of one or more classes. rdf:type is an instance of rdf:Property that is used tordf:type state that a resource is an instance of a class. The property rdfs:subClassOf is an instance ofrdfs:subClassOf rdf:Property that is used to state that all the instances of one class are instances of another. The property rdfs:subPropertyOf is an instance ofrdfs:subPropertyOf rdf:Property that is used to state that all resources related by one property are also related by another. www.iks-project.eu Copyright IKS Consortium
  21. 21. Page: 21 RDFS Constructs – Predefined Properties (II) rdfs:label is an instance of rdf:Property that may berdfs:label used to provide a human-readable version of a resources name. rdfs:comment is an instance of rdf:Property that mayrdfs:comment be used to provide a human-readable description of a resource. www.iks-project.eu Copyright IKS Consortium
  22. 22. Page: 22 RDFS - Example classclass ex:Company ex:Vehicle rdf:range rdfs:domain rdfs:subClassOf ex:Brand rdfs:subClassOfclass property ex:Car class ex:CarManufacturer RDFS rdf:type Terminological knowledge RDF rdf:type Assertional knowledge ex:Brand ex:myCar ex:Jaguar www.iks-project.eu Copyright IKS Consortium
  23. 23. Page: 23 Back to the Cake ...A language for queryinginformation specified in A language for describing a RDF. lightweight ontology. A model for describingresources with properties A format for specifying structured and property values. data in a machine-readable form Unique identification of resources Semantic Web Layer Cake, Image source: http://www.w3.org/2007/03/layerCake.svg www.iks-project.eu Copyright IKS Consortium
  24. 24. Page: 24 Why is RDFS not enough? RDFS cannot express negations Defined property restrictions are global Missing cardinalities for properties Relations between (sub-)classes (e.g. disjunction) www.iks-project.eu Copyright IKS Consortium
  25. 25. Page: 25 OWL – Web Ontology Language “The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans.” OWL has been developed as a vocabulary extension of RDF Explicitly represents the meaning of terms in vocabularies and the relationships between those terms. (Ontology) http://www.w3.org/TR/2004/REC-owl-features-20040210/ www.iks-project.eu Copyright IKS Consortium
  26. 26. Page: 26 OWL – The Story 2004 - OWL W3C Recommendation 2009 - OWL 2 W3C RecommendationOWL = Web Ontology Language Why not WOL?  Obvious pronunciation which is easy on the ear http://piqs.de  Opens up great opportunities for logos  Owls are associated with wisdom  It has an interesting back story http://lists.w3.org/Archives/Public/www-webont-wg/2001Dec/0169.html www.iks-project.eu Copyright IKS Consortium
  27. 27. Page: 27 Dialects of OWL OWL Lite  Provides classification hierarchy and simple constraint features OWL DL (description logic) - Includes OWL Lite  Provides the maximum expressiveness without losing computational completeness and decidability of reasoning systems. OWL Full - Includes OWL DL  Is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees. http://www.w3.org/TR/2004/REC-owl-features-20040210/ www.iks-project.eu Copyright IKS Consortium
  28. 28. Page: 28 How does OWL look like? RDF Document Basic structure of an OWL Document Namespace Definitions<rdf:RDF xmlns:owl ="http://www.w3.org/2002/07/owl#" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#" Default Namespace xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:xsd ="http://www.w3.org/2001/XMLSchema#"> xmlns="http://example.org/"> Ontology Header <owl:Ontology rdf:about=“”> <rdfs:comment>An example OWL ontology</rdfs:comment> <owl:priorVersion rdf:resource="http://example.org/20120101/cars"/> <owl:imports rdf:resource="http://example.org/20110707/manufacturer"/> <rdfs:label>Car Ontology</rdfs:label> </owl:Ontology> Importing another... ontology</rdf:RDF> www.iks-project.eu Copyright IKS Consortium
  29. 29. Page: 29 Simple OWL Classes Comparable to RDFS classes Every individual in OWL is a member of the class owl:Thing Each user-defined class is implicitly a subclass of owl:Thing OWL also defines the empty class owl:Nothing Definition of domain-specific root classes: <owl:Class rdf:ID=“Vehicle”/> <owl:Class rdf:ID=“CarManufacturer”/> Define class www.iks-project.eu Copyright IKS Consortium
  30. 30. Page: 30 Hierarchies of Classes Thedefinition of basic taxonomies for classes can be done by rdfs:subClassOf. rdfs:subClassOf is transitive. “Car” is a subclass of “Vehicle” <owl:Class rdf:ID=“Car"> <rdfs:subClassOf rdf:resource="Vehicle"/> </owl:Class> www.iks-project.eu Copyright IKS Consortium
  31. 31. Page: 31 Disjoint Classes “The disjointness of a set of classes can be expressed using the owl:disjointWith constructor. It guarantees that an individual that is a member of one class cannot simultaneously be an instance of a specified other class.“ The classes “Car” and “Vehicle” are disjoint. <owl:Class rdf:about=“Car"> <owl:disjointWith rdf:resource=“Cat”/> </owl> www.iks-project.eu Copyright IKS Consortium
  32. 32. Page: 32 Infer about Disjoint Classes The class “Car” is a <owl:Class rdf:ID=“Car"> subclass of “Vehicle” <rdfs:subClassOf rdf:resource="Vehicle"/> </owl:Class> The class “Cat” is a <owl:Class rdf:ID=“Cat"> subclass of “Animal” <rdfs:subClassOf rdf:resource=“Animal"/> </owl:Class> The classes <owl:Class rdf:about=“Vehicle"> “Vehicle” and <owl:disjointWith rdf:resource=“Animal”/> “Animal” are disjoint </owl>It can be inferred, that the classes “Car” and “Cat“are disjoint too! www.iks-project.eu Copyright IKS Consortium
  33. 33. Page: 33 Individuals  In addition to the definition of classes, we also need to describe the members of classes (individuals) Definition of <owl:Thing rdf:ID=“Jaguar"/> individual “Jaguar” <owl:Thing rdf:about=“Jaguar"> <rdf:type rdf:resource=“CarManufacturer"/> </owl:Thing>Ties the individual to the class  Abbreviated representation < CarManufacturer rdf:ID="Jaguar"/> www.iks-project.eu Copyright IKS Consortium
  34. 34. Page: 34 Simple Properties “This world of classes and individuals would be pretty uninteresting if we could only define taxonomies. Properties let us assert general facts about the members of classes and specific facts about individuals.“ Property are binary relations. In OWL, two different types of properties are distinguished:  object properties, relations between instances of two classes.  datatype properties, relations between instances of classes and RDF literals and XML Schema datatypes http://www.w3.org/TR/owl-guide/ www.iks-project.eu Copyright IKS Consortium
  35. 35. Page: 35 Object Properties Objectproperties relate instances of classes by rdfs:domain and rdfs:range. Properties are <owl:ObjectProperty rdf:about=“Brand”/> defined like classes Domain and range <owl:ObjectProperty rdf:ID=“Brand”> for object property <rdfs:domain rdf:resource=“Vehicle”/> “Brand” <rdfs:range rdf:resource=“CarManufacturer”/> </owl:Thing> www.iks-project.eu Copyright IKS Consortium
  36. 36. Page: 36 Datatype Properties Datatypeproperties relate class instances and data values using rdfs:domain and rdfs:range. Properties are defined like classes <owl:DatatypeProperty rdf:about=“ConstructionYear”/> Domain and range for <owl:ObjectProperty rdf:ID=“ConstructionYear”> datatype property <rdfs:domain rdf:resource=“Car”/> “ConstructionYear” <rdfs:range rdf:resource=“&xsd;gYear”/> </owl:Thing> http://www.w3.org/TR/owl-guide/ www.iks-project.eu Copyright IKS Consortium
  37. 37. Page: 37 Recommended XML Schema datatypesxsd:string xsd:normalizedString xsd:booleanxsd:decimal xsd:float xsd:doublexsd:integer xsd:nonNegativeInteger xsd:positiveIntegerxsd:nonPositiveInteger xsd:negativeInteger xsd:bytexsd:long xsd:int xsd:shortxsd:unsignedLong xsd:unsignedInt xsd:unsignedShortxsd:hexBinary xsd:base64Binary xsd:unsignedBytexsd:dateTime xsd:time xsd:datexsd:gYear xsd:gMonthDay xsd:gDayxsd:anyURI xsd:token xsd:languagexsd:NMTOKEN xsd:Name xsd:NCNamexsd:gYearMonth xsd:gMonth www.iks-project.eu Copyright IKS Consortium
  38. 38. Page: 38 Cardinality Constraints for Properties owl:minCardinality defines the minimal cardinality for the value of a property. owl:maxCardinality defines the maximal cardinality for the value of a property. <owl:Class rdf:ID=“Vehicle"> Anonymous class Restriction for <rdfs:subClassOf> property “Wheels” <owl:Restriction> <owl:onProperty rdf:resource=“Wheels”/> <owl:minCardinality rdf:datatype=“&xsd;nonNegativeInteger”>2 </owl:minCardinality> </owl:Restriction> </rdfs:subClassOf> Minimal number of </owl:Class> “Wheels” is “2” www.iks-project.eu Copyright IKS Consortium
  39. 39. Page: 39 Cardinality Constraints for Properties “owl:cardinality permits the specification of exactly the number of elements in a relation.” <owl:Class rdf:ID=“Motorcycle"> Restriction for <rdfs:subClassOf> property “Wheels” <owl:Restriction> <owl:onProperty rdf:resource=“Wheels”/> <owl:cardinality rdf:datatype=“&xsd;nonNegativeInteger”>2 </owl:cardinality> </owl:Restriction> </rdfs:subClassOf> Exact number of </owl:Class> “Wheels” is “2” www.iks-project.eu Copyright IKS Consortium
  40. 40. Page: 40 Property Restrictions “The owl:allValuesFrom restriction requires that for every instance of the class that has instances of the specified property, the values of the property are all members of the class indicated by the owl:allValuesFrom clause.” Restriction on property Local restriction for class definition “PreOwner“ for instances from class <owl:Class rdf:ID=“Car"> <rdfs:subClassOf> “Car” <owl:Restriction> <owl:onProperty rdf:resource=“preOwner” /> <owl:allValuesFrom rdf:resource=“Person” /> </owl:Restriction> <rdfs:subClassOf> </owl:Class> Each value is member of class “Person” Copyright IKS Consortium www.iks-project.eu
  41. 41. Page: 41 Property Restrictions Restriction on property <owl:Class rdf:ID=“Car"> “PreOwner“ for instances from class <rdfs:subClassOf> “Car” <owl:Restriction> <owl:onProperty rdf:resource=“preOwner” /> <owl:someValuesFrom rdf:resource=“Person” /> </owl:Restriction> <rdfs:subClassOf> At least one value is </owl:Class> member of class “Person” Relation ImplicationallValuesFrom For all cars, if they have a previous owner, all previous owners are persons.someValuesFrom For all cars, they have at least one previous owner that is a person. www.iks-project.eu Copyright IKS Consortium
  42. 42. Page: 42 Property Restrictions with Constants “owl:hasValue allows us to specify classes based on the existence of particular property values. Hence, an individual will be a member of such a class whenever at least one of its property values is equal to the owl:hasValue resource.” <owl:Class rdf:ID=“myCars"> Restriction for <rdfs:subClassOf> property “Owner” <owl:Restriction> <owl:onProperty rdf:resource=“Owner”/> <owl:hasValue rdf:”JohnMiller”> </owl:Restriction> </rdfs:subClassOf> </owl:Class> The class “myCar” is defined by value www.iks-project.eu assignment Copyright IKS Consortium
  43. 43. Page: 43 Intersection owl:intersectionOf defines a class as an intersection of other classes.<owl:Class rdf:ID=“CarsFromVW"> <owl:intersectionOf rdf:parseType=“Collection”> <owl:Class rdf:about=”Cars”> <owl:Class rdf:about=“VW”/> If something is a “Car” </owl:intersectionOf> and a “VW” it is a</owl:Class> ”CarFromVW” www.iks-project.eu Copyright IKS Consortium
  44. 44. Page: 44 Union “owl:unionOf describes a class that contains those individuals that occur in at least one of the class Gearbox is everything that extensions of the class descriptions in the list”. is “ManualTransmission” or <owl:Class rdf:ID=“Gearbox"> “AutomaticTransmission”. <owl:unionOf rdf:parseType=“Collection”> <owl:Class rdf:about=”ManualTransmission”> <owl:Class rdf:about=“AutomaticTransmission”/> </owl:intersectionOf> </owl:Class> www.iks-project.eu Copyright IKS Consortium
  45. 45. Page: 45 Complement “The owl:complementOf construct selects all individuals from the domain of discourse that do not belong to a certain class.” <owl:Class rdf:about=”ManualTransmission”> <owl:Class rdf:about=“AutomaticTransmission”/> </owl:complementOf ref:resource=“ManualTransmission” /> </owl:Class> “AutomaticTransmission” includes as members all individuals that do not belong to “ManualTransmission”. www.iks-project.eu Copyright IKS Consortium
  46. 46. Page: 46 If you want to know more ... There is stuff about OWL out there, which is not part of this course:  Class axioms  Global restriction for properties  Logical characteristics of properties Ifyou are interested in learning more about OWL please check:  The W3C OWL Reference (http://www.w3.org/TR/owl-ref)  The W3C OWL Guide (http://www.w3.org/TR/owl-guide) www.iks-project.eu Copyright IKS Consortium
  47. 47. Page: 47 OWL 2 OWL 2 adds new functionality to OWL, while the overall structure is very similar OWL 2 provides syntactic sugar  e.g. disjoint union of classes Some OWL 2 feature provide new expressivity:  keys, property chains  richer datatypes, data ranges;  qualified cardinality restrictions  asymmetric, reflexive, disjoint properties  enhanced annotation capabilities http://www.w3.org/TR/owl2-primer/ www.iks-project.eu Copyright IKS Consortium
  48. 48. Page: 48 Back to the Cake ... Highly expressive ontology language for modelling complexA language for querying knowledge domains.information specified in RDF. A language for describing a lightweight ontology. A model for describingresources with properties A format for specifying structured and property values. data in a machine-readable form Unique identification of resources Semantic Web Layer Cake, Image source: http://www.w3.org/2007/03/layerCake.svg www.iks-project.eu Copyright IKS Consortium
  49. 49. Page: 49 Lessons Learned Now you should know ...  ... what is the main difference between RDF and ontology languages like RDF Schema and OWL.  ... how can RDF Schema be used to build simple ontologies.  ... what are the shortcomings of RDF Schema and why is it not enough in some application cases.  ... the web ontology language OWL.  .. in which sense OWL is more expressive than RDF Schema. www.iks-project.eu Copyright IKS Consortium
  50. 50. Page: 50 References and Additional Material RDFVocabulary Description Language 1.0: RDF Schema  http://www.w3.org/TR/rdf-schema/ OWL Web Ontology Language Guide  http://www.w3.org/TR/owl-guide/ OWL Web Ontology Language Reference  http://www.w3.org/TR/owl-ref/ OWL 2 Web Ontology Language Primer  http://www.w3.org/TR/owl2-primer/ www.iks-project.eu Copyright IKS Consortium

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