Axel Polleres (DERI, National University of Ireland)
As the data and ontology layers of the Semantic Web stack have achieved a certain level of maturity in standard recommendations such as RDF and OWL, the current focus lies on two related aspects. On the one hand, the definition of a suitable query language for RDF, SPARQL, seems to be close to candidate recommendation status within the W3C. The establishment of the Rules layer on top of the existing stack on the other hand marks the next step to be tackled, where especially languages with their roots in Logic Programming and Deductive Databases are receiving considerable attention. The purpose of this paper is threefold. First, we discuss the formal semantics of SPARQL extending recent results in several ways. Second, we provide translations from SPARQL to Datalog with stratified negation as failure. Third, we propose some useful and easy to implement extensions of SPARQL, based on this translation. As it turns out, the combination serves for direct implementations of SPARQL on top of existing rules engines as well as a basis for more general rules and query languages on top of RDF.
New Brunswick, Friday, May 11, 2007, 3:30pm to 5:00pm.