Is Your Ontology as Hard as You Think? Rewriting Ontologies into Simpler DLs

Abstract. We investigate cases where an ontology expressed in a seem-ingly hard DL can be polynomially reduced to one in a simpler logic, while preserving reasoning outcomes for classification and fact entail-ment. Our transformations target the elimination of inverse roles, uni-versal and existential restrictions, and in the best case allow us to rewrite the given ontology into one of the OWL 2 profiles. Even if an ontology cannot be fully rewritten into a profile, in many cases our transforma-tions allow us to exploit further optimisation techniques. Moreover, the elimination of some out-of-profile axioms can improve the performance of modular reasoners, such as MORe. We have tested our techniques on both classification and data reasoning tasks with encouraging results.