WSML Deliverable D 20 . 1 v 0 . 2 OWL Flight WSML Working Draft

This deliverable presents a restricted variant of the OWL Lite species of the OWL ontology language, called OWL Lite−. OWL Lite− is a strict subset of OWL Lite and can be translated directly into the deductive database language Datalog. Thus, any OWL Lite− ontology can be translated into Datalog, in order to allow for efficient query answering. It turns out that most current ontologies fall inside this fragment. An ontology language for which a translation to Datalog exists has several advantages. Most notably, it can benefit from highly optimized query answering engines, and allows for easy implementation of a rule and a query language on top of the ontology. We describe the restrictions on the OWL Lite abstract syntax and provide an analysis of the features of OWL Lite, which are not included in OWL Lite−, and give a rationale for not including them in the language. We present the RDF syntax and the model-theoretic semantics for OWL Lite− and relate OWL Lite− with RDFS. Finally, we indicate possible future extensions of the language. Copyright c © 2004 DERI R © , All Rights Reserved. DERI liability, trademark, document use, and software licensing rules apply. D20.1 – OWL Flight 3