The Web of Data is an open environment consisting of very large, inter-linked RDF datasets from various domains (e.g., DBpedia, GeoNames, ACM, PubMed, etc.) accessed through SPARQL queries. Establishing interoperability in this environment has become a major research challenge. This paper presents Sparql--Rw (SPARQL--ReWriting), a framework which provides transparent query access over mapped RDF datasets. The Sparql--Rw provides a generic method for SPARQL query rewriting, with respect to a set of predefined mappings between ontology schemas. To this end, it supports a set of rich and flexible mapping types and it is proved to provide semantics preserving queries.