Abstract:
OWL-DL is a World Wide Web Consortium standard for representing ontologies on the Semantic Web. It can be seen as a syntactic variant of the Description Logic SHOIN(D), with an OWL-DL ontology corresponding to a SHOIN(D) knowledge base. The very recent accomplishment of a decision procedure for SHOIN(D) poses the challenge of turning the decision procedure into a practical implementation. In particular, we emphasize the need of new optimization techniques for nominals, especially in the presence of large number of individuals in the KB. In this paper, we present new techniques for optimizing DL reasoning in the presence of nominals in the TBox and individuals in a large ABox. We have integrated our optimizations in the open-source Pellet reasoner, which is sound and complete for SHOIN(D), and found that they suffice for efficiently classifying the famous Wine Ontology. We also show that these optimization techniques produce significant performance improvements in other widely used ontologies containing nominals, such as the OWL-S and AKT ontologies.