Web Ontology Language: OWL OWL documents are usually called OWL ontologies, and are RDF documents So the root element of a OWl ontology is an rdf: RDF element which als specifies a number of namespaces. For example xmlns:owl=http://www.w3.org/2002/07/owl# xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#" //www xmlns:xsd=http://www.w3.org/2001/xlmschema#"> An OWL ontology may start with a collection of assertions for hous keeping purposes. These assertions are grouped under an owl: Ontology ele- ment which contains comments version control and inclusion of other ontolo- gies. For example <owl: Ontology rdf: about=> <rdfs: comment>An example OWL ontology </rdfs: comment> <owl: priorVersion rdfresource="http://www.mydomain.org/uni-ns-old"/ <owl:importsrdfresource="http://www.mydomain.org/persons"/> <rdfs: label>University Ontology</rdfs: label> </owl: Ontology> The only of these assertions which has any consequences for the logical meaning of the ontology is owl: imports: this lists other ontologies whose content is assumed to be part of the current document ontology. Notice that while namespaces are used for disambiguation purposes, imported ontologies provide definitions that can be used. Usually there will be an import element for each used namespace, but it is possible to import additional ontologies for example ontologies that provide definitions without introducing any new Also note that owl: imports is a transitive property: if ontology A imports B and ology C Class elements Classes are defined using a owl: Class element. For example, we can define <owl: Class rdf: ID=associat r"> academicStaffMember"/> </owl: Class> owl: Class is a subclass of rdfs: ClassWeb Ontology Language: OWL 7 Header OWL documents are usually called OWL ontologies, and are RDF documents. So the root element of a OWL ontology is an rdf:RDF element which also specifies a number of namespaces. For example: <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/XLMSchema#"> An OWL ontology may start with a collection of assertions for house￾keeping purposes. These assertions are grouped under an owl:Ontology ele￾ment which contains comments, version control and inclusion of other ontolo￾gies. For example: <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> The only of these assertions which has any consequences for the logical meaning of the ontology is owl:imports: this lists other ontologies whose content is assumed to be part of the current document. ontology. Notice that while namespaces are used for disambiguation purposes, imported ontologies provide definitions that can be used. Usually there will be an import element for each used namespace, but it is possible to import additional ontologies, for example ontologies that provide definitions without introducing any new names. Also note that owl:imports is a transitive property: if ontology A imports ontology B, and ontology B imports ontology C, then ontology A also imports ontology C. Class elements Classes are defined using a owl:Class element 7 . For example, we can define a class associateProfessor as follows: <owl:Class rdf:ID="associateProfessor"> <rdfs:subClassOf rdf:resource="#academicStaffMember"/> </owl:Class> 7 owl:Class is a subclass of rdfs:Class