Efficient query answering in DL-lite through FOL reformulation

We propose a general query optimization framework for formalisms enjoying FOL reducibility of query answering, for which it reduces to the evaluation of a FOL query against facts. This framework allows searching within a set of alternative equivalent FOL queries, i.e., FOL reformulations, one with minimal evaluation cost when evaluated through a relational database management system. We provide two algorithms, an exhaustive and a greedy, for exploring the optimization space. This framework is applied to the lightweight description logic DL-LiteR underpinning the W3C's OWL2 QL profile, for which an experimental evaluation validates the interest and applicability of our technique.