Query Rewriting Under Ontology Evolution ⋆

Abstract. One of the most prominent reasoning techniques for query answering is query rewriting. The last years a wide variety of query rewriting systems has been proposed. All of them accept as input a CQ Q and a fixed ontology O and produce a rewriting for Q, O. However, in many real world applications ontologies are very often dynamic—that is, new axioms can be added or existing ones removed frequently. In this paper we study the problem of computing a rewriting for a CQ over an ontology that has been evolved (i.e., a set of new axioms has been added to O), by exploiting the information computed for the extraction of the initial rewriting. Our goal is to avoid computing the target rewriting from scratch or repeating computations that have already been conducted for the initial rewriting. We study the problem theoretically and we specify the form that the input information must have for the efficient computation of the new rewriting based on some of the known query rewriting systems (QuOnto, Requiem, Rapid, Naya). Moreover, we present a practical algorithm which we implemented and evaluated against the query rewriting system Requiem obtaining encouraging results