Web Ontology Language: OWL - Vrije Universiteit Amsterdam

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Web Ontology Language: OWL - Vrije Universiteit Amsterdam

8 Grigoris Antoniou and Frank van HarmelenWe can also say that this class is disjoint from the professor andassistantProfessor classes using owl:disjointWith elements. These elementscan be included in the definition above, or can be added by referringto the id using rdf:about. This mechanism is inherited from RDF.Equivalence of classes can be defined using a owl:equivalentClass element:Finally, there are two predefined classes, owl:Thing and owl:Nothing. Theformer is the most general class which contains everything (everything isa thing), the latter is the empty class. Thus every class is a subclass ofowl:Thing and a superclass of owl:Nothing.Property elementsIn OWL there are two kinds of properties:• Object properties which relate objects to other objects.Examples are isTaughtBy, supervises etc.• Datatype properties which relate objects to datatype values.Examples are phone, title, age etc. OWL does not have any predefineddata types, nor does it provide special definition facilities. Instead it allowsone to use XML Schema data types, thus making use of the layeredarchitecture the Semantic WebHere is an example of a datatype property.User-defined data types will usually be collected in an XML schema, and thenused in an OWL ontology.Here is an example of an object property:

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