RDF Schema (RDFS) is an extension
of RDF that contains supplementary predicates that allows the definition
of more structure than RDF (Colomb, 2005). RDFS makes it possible to define a
class, subclass, and with an instance being defined using rdfs:Class, rdfs:subClassOF
and rdf:type respectively, as shown in Figure 5. RDF can be used in isolated
applications, where individually designed formats might be more direct and easily
understood, but RDFS generality offer greater value from sharing (Colomb, 2005;
Klyne & Carroll, 2004).
OWL is a specialisation of RDF also developed by the W3C designed to be compatible
with putting ontologies on the Web. OWL is used when the information is intended
to be machine processed and can be used to represent an ontology, (McGuinness &
Figure 2. OWL classes developed in Prot?©g?©
Blake and Pease
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission
of Idea Group Inc. is prohibited.
Van Harmelen, 2004) as the RDF structure is unable to support a reasoner (Colomb,
2005). OWL extends RDFS by allowing the defining of complex relationships
between different RDFS classes and contains the facility to more accurately place
constraints on classes and properties.
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