1. A method of integrating an RDF pattern that specifies a subset of a set of RDF triples into an SQL query on a relational database system, the set of RDF triples being accessible to the relational database system and the method comprising the steps performed in the relational database system of: receiving a containing SQL query that includes the RDF pattern; and during execution of the containing query, obtaining results that are equivalent to the subset of RDF triples specified by the RDF pattern from the set of RDF triples and providing a set of rows with the obtained results to the containing query.