Efficiently Querying RDF(S) Ontologies with Answer Set Programming

Ontologies are pervading many areas of knowledge representation and management. To date, most research efforts have been spent on the development of sufficiently expressive languages for the representation and querying of ontologies; however, querying efficiency has received attention only recently, especially for ontologies referring to large amounts of data. In fact, it is still uncertain how reasoning tasks will scale when applied on massive amounts of data. This work is a first step toward this setting: it first shows that RDF(S) ontologies can be expressed, without loss of semantics, into Answer Set Programming (ASP). Then, based on a previous result showing that the SPARQL query language (a candidate W3C recommendation for RDF(S) ontologies) can be mapped to a rule-based language, it shows that efficient querying of big ontologies can be accomplished with a database oriented extension of the well known ASP system DLV, which we recently developed. Results reported in the paper show that our proposed framework is promising for the improvement of both scalability and expressiveness of available RDF(S) storage and query systems. 1Institut für Informationssysteme 184/3, Technische Universität Wien, Favoritenstraße 9-11, A-1040 Vienna, Austria. 2Dipartimento di Matematica, Università della Calabria, I-87036 Rende (CS), Italy. Acknowledgements: The work of the first author has been supported under FWF projects P20841 (Modular HEX-Programs), P17212 (Answer Set Programming for the Semantic Web), and MIUR (Italian Research Ministry) Interlink II04CG8AGG. We gratefully acknowledge Axel Polleres (DERI-Galway) for his insightful comments and for providing a prototypical version of the SPARQL-Datalog translator. To appear on Journal of Logic and Computation, Oxford University Press, Oxford, UK. doi:10.1093/logcom/exn043 Copyright c © 2008 by the authors 2 INFSYS RR RR-1843-08-06