Distributed island-based query answering for expressive ontologies

Abstract. Scalability of reasoning systems is one of the main criteria which will determine the success of Semantic Web systems in the future. The focus of recent work is either on (a) expressive description logic sys-tems which rely on in-memory structures or (b) not-so-expressive ontol-ogy languages, which can be dealt with by using database technologies. In this paper we introduce a method to perform query answering for semi-expressive ontologies without the limit of in-memory structures. Our main idea is to compute small and characteristic representations of the assertional part of the input ontology. Query answering is then more efficiently performed over a reduced set of these small representations. We show that query answering can be distributed in a network of description logic reasoning systems in order to support scalable reasoning. Our initial results are encouraging.