Status QIO: Conjunctive Query Entailment is Decidable
Published: 2010 Mai
Buchtitel: Principles of Knowledge Representation and Reasoning: Proceedings of the Eleventh International Conference
Verlag: AAAI Press
Description Logics (DLs) are knowledge representation formalisms that provide, for example, the logical underpinning of the W3C OWL standards. Conjunctive queries (CQs), the standard query language in databases, have recently gained significant attention for querying DL knowledge bases. Several different techniques are available for a wide range of DLs. Nevertheless, for OWL DL and OWL 2, decidability of CQ entailment is an open problem. So far, the combination of nominals, inverse roles, and number restrictions caused unsolvable problems. We tackle this problem and present a decidability result for entailment of unions of CQs in a DL with all three problematic constructors. For queries with only simple roles, our result also shows decidability in the logic that underpins OWL DL and we believe that the presented results will pave the way for further progress towards CQ entailment decision procedures for OWL DL and OWL 2.