The Combined Approach to Query Answering in Horn-ALCHOIQ.

Combined approaches have become a successful technique for solving conjunctive query (CQ) answering over description logics (DL) ontologies. Nevertheless, existing approaches are restricted to tractable DL languages. In this work, we extend the combined method to the more expressive DL Horn-ALCHOIQ-a language for which CQ answering is EXPTIME-complete-in order to develop an efficient and scalable CQ answering procedure which is worst-case optimal for Horn- ALCHOIQ and ELHO ontologies. We implement and study the feasibility of our algorithm, and compare its performance to the DL reasoner Konclude.