Querying Heterogeneous Relational Database using SPARQL

The emergence of the semantic Web has given rise to several researches on semantic integration of heterogeneous relational databases using ontology. This paper studies the query rewriting problem in such an integration scenario. RDFpsilas graph model lends itself well to expressing relational data. To model the relational schema, we propose a data source describing method based on SPARQL graph patterns and give some principles for semantic mapping between relational schema and RDF ontology. The semantic of query rewriting is further discussed and a query rewriting algorithm is presented so that SPARQL can access heterogeneous relational databases without converting the data into physical triples.