SPARQL & Object-Relational Mapping Tools

Hello,

I'm looking for tools that covert from SPARQL to HQL (Hibernate Query
Language). Can anyone on this list recommend something?

I'm familiar with the work of Guillaume Hillaret, et al, in "Rewriting
Queries by Means of Model Transformations from SPARQL to OQL and Vice-Versa"
and Walter Corno et al in "Exposing Heterogeneous Data Sources as SPARQL
Endpoints through an Object-Oriented Abstraction", but neither of these
approaches is very mature.

I'm also familiar with RDF-RDBM mapping tools (e.g. D2R Server, Virtuoso RDF
Views, etc). But these don't seem appropriate for exposing applications that
primarily manage data through object-relational (OR) mapping tools because
the relational schema doesn't closely reflect entities in the
object-oriented information model.

Are there mature tools for bridging translating queries over and RDF mode to
queries over an object-oriented model?

Thanks in advance for your suggestions and insights.

 - Joshua