Revelytix will be releasing Spyder, a relational to RDF run time tool, in March 2011. Spyder will use the Revelytix mapping ontology at run time to execute the relational to RDF conversion in real time. The mapping ontology was built before the R2RML working group had narrowed in on a solution to this problem. When Spyder is released we will change our mapping ontology to support the R2RML work as it currently stands. When a final recommendation is achieved by this working group, we will support the final recommendation.
The Mapping Ontology can be found at the link above. Revelytix maintains the Mapping Ontology and Relational Schema Ontology, along with descriptions and examples of the usage of these ontologies as open source ontologies. These ontologies are used in conjunction with the Revelytix Spyder to allow you to query any relational database as a SPARQL endpoint.