Sparql Rules! Sparql Rules!

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 taken, 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. A prototype implementation is available for evaluation of our approach. ∗This report is an extended version of the paper titled “From SPARQL to Rules (and back)” to appear inWWW2007. It is a slight update of the original report published at http://www.polleres.net/publications/GIA-TR-2006-11-28.pdf on 2006-11-28 with minor typo fixes and encompasses reviewer comments for the conference version. Copyright c © 2006 by the author