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Web Ontology Language

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Semantic Web in Depth Web Ontology Language (OWL) Dr Nicholas Gibbins - [email protected] 2011-2012 1 For many, RDF Schema is a sufficiently expressive ontology language However, there are use cases which require a more expressive formalism: Instance classification Consistency checking Subsumption reasoning Introducing OWL 2 OWL Feature Summary Necessary and sufficient conditions for class membership Property restrictions Local range, cardinality, value constraints Equivalence and identity relations Property characteristics Transitive, symmetric, functional Complex classes Set operators, enumerated classes, disjoint classes 3 OWL Versions Two versions of OWL: OWL 1.0 (became Recommendation on 10 Feb 2004) OWL 2 (became Recommendation on 29 Oct 2009) OWL 2 is more expressive than OWL 1.0, and takes advantage of developments in DL reasoning techniques in the intervening time We will initially concentrate on OWL 1.0 Brachman, R. J., and H. J. Levesque. (1984). The tractability of subsumption in frame-based description languages. In Proceedings of the 4th National Conference of the American Association for Artificial Intelligence (AAAI-84). Austin, TX, pp. 34-37. OWL 1.0 Species Different subsets of OWL features give rise to the following sublanguages (colloquially known as species): OWL Lite OWL DL OWL Full “There is a tradeoff between the expressiveness of a representation language and the difficulty of reasoning over the representations built using that language.” 5 OWL 1.0 Species RDF(S) OWL Lite OWL DL OWL Full Increasing expressivity Increasing complexity 6 OWL Lite Description Logic-based SHIF(D) Less complex reasoning at the expense of less expressive language No enumerated classes, set operators, or disjoint classes Restricted cardinality restrictions (values of 0 or 1 – required, permitted and excluded) No value restrictions equivalentClass/subClassOf cannot be applied to class expressions 7 OWL DL Description Logic-based SHOIN(D) Complete and decidable Higher worst-case

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