Connect RDF to PostgreSQL?

I am presenting on PostgreSQL tonight and someone e-mailed me with a
question before my talk so I might be able to find him an answer:

"We are starting a new, large project that uses an ontology based (
RDF - Resource Description Framework
http://en.wikipedia.org/wiki/Resource_Description_Framework ) approach
to organize data, which provides a lot of flexibility. The only viable
database we have found that supports this is Oracle, who have tightly
integrated their database interface to efficiently support sparql (
http://en.wikipedia.org/wiki/SPARQL ) queries. Other databases seem to
only interface to the open source jena technology, which fails to
scale to larger data sets as it tries to read huge chunks of data into
memory.

We would prefer to go with an open source option, but can't. Do you
know of a software package that can efficiently connect RDF to
PostgreSQL?"

Aaron Thul
http://www.chasingnuts.com