On the Semantics of SPARQL

The Resource Description Framework (RDF) is the standard data model for representing information about World Wide Web resources. Jointly with its release as Recommendation of the W3C, the natural problem of querying RDF data was raised. In the last years, the language SPARQL has become the standard query language for RDF and, in fact, a W3C Recommendation since January 2008. In this paper, the authors give a detailed description of the semantics of SPARQL. They start by focusing on the definition of a formal semantics for the core part of SPARQL, and then move to the definition for the entire language, including all the features in the specification of SPARQL by the W3C such as blank nodes in graph patterns and bag semantics for solutions.