12 Dec. 2006 CmpE 583 Fall 2006 Basic OWL Lite 1

Basic OWL Lite off TextbookCh. 12: Classes & Properties

Atilla Elçi

12 Dec. 2006 CmpE 583 Fall 2006 Basic OWL Lite 2

Basic OWL Lite• Involves class and property declarations.• Class:

– Represents domains in OWL– Subclass of rdfs:Class– Two kinds:

• Simple Named Classes• Predefined Classes

• Property:– Associates values with individuals– By relating individuals to datatype or another individual– Can be a class to representing variety of property specification– Relates an instance of a domain to an instance of a range– There are four disjoint types of properties in OWL Lite:

• Datatype• Object• Annotation• Ontology properties.

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Basic OWL Lite: Classes

Simple Named Class (owl:Class):• Classes are named using upper CamelCase• User defines a simple named class as follows:

<owl:Class rdf:ID=“MyOntologyClass”/>or, may include class properties as well.• rdf:ID signals that a new resource is being

defined.• Ref to a class:

– Internally by URIRef fragment: #MyOntologyClass– Externally by full URIRef.

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Basic OWL Lite: Classes (continued)

Predefined Classes (Extreme Classes):• Thing Class (owl:Thing):

– A super class for all classes• Every individual is a member• Every class is a subclass• Everything about owl:Thing applies to everything!• Can use typed node syntax:

instead of rdf:resource=“URIRef” use <rdf:Thing rdf:about=“URIRef” />

• Nothing Class (owl:Nothing):– Subclass of all classes– Empty class (has no individual members).

12 Dec. 2006 Rev. 23/12/08

CmpE 583 Fall 2006 Basic OWL Lite 5

Basic OWL Lite: PropertiesThere are four disjoint types of properties in OWL Lite:

– Datatype– Object– Annotation– Ontology properties <owl:Ontology rdf:about=“URI”> where “URI” is either:

• Each type is a subclass of rdf:Property• Datatype Property (owl:DatatypeProperty) class:

– Identifies a property whose value is associated with a datatype such as literal rather than resources.

– For example, in defining sessionStartTime as a datatype property type:<owl:DatatypeProperty rdf:ID=“sessionStartTime”>

<rdfs:domain rdf:resource=“#Lecture” /><rdfs:range rdf:resource=“&xsd;time”>

</owl:DatatypeProperty>– The use of this property type:

<sessionStartTime rdf:datatype=“&xsd;time”>8:30:00:00+01:00</session...>

– Compare that with the following: rdf:about=“...”<train:Lecture rdf:ID=“CmpE583”>

<startTime>8:30:00+01:00</startTime></train:Lecture>

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Basic OWL Lite: Properties (continued)

• Object Properties (owl:ObjectProperty) class:– Identifies a property whose value is a reference to an individual

(resource).– For example, in defining taughtBy as an object property:

<owl:ObjectProperty rdf:ID=“taughtBy”/>– The use of this property could be:

<Person rdf:ID=“aelci”><givenName>Atilla</givenName>

</Person><train:Lecture rdf:ID=“CmpE583”>

<rdfs:label>Web Semantics</rdfs:label ><startTime>8:30:00+01:00</startTime ><taughtBy rdf:resource=“#aelci” />

</train:Lecture>

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Basic OWL Lite: Properties (continued)

• Annotation Properties (owl:AnnotationProperty) class:– Identifies a special type of property whose value is a named class,

property, individual, or ontology.– For example, in defining annotation property on taughtBy (referred to as

a URIRef):<owl:AnnotationProperty rdf:about=“#taughtBy” >

<propertyX .... /><propertyY .... />

</owl:AnnotationProperty>– There are predefined OWL annotation properties:

• rdfs:label• rdfs:comment• rdsf:seeAlso• rdfs:isDefinedBy• owl:versionInfo

12 Dec. 2006 Rev. 23/12/08

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Basic OWL Lite: Properties (continued)

• Ontology Properties (owl:OntologyProperty) class:– Identifies a type of property which relates to

ontologies.– There are predefined OWL ontology

properties: • owl:imports• owl:backwardCompatibleWith• owl:incompatibleWith• owl:priorVersion