Searching the link module issue queue for the text "duplicate" brought about a few others working on this feature.
The RDF SPARQL Endpoint module indexes the RDF data publicly available on a Drupal site into an ARC2 RDF store. It also provides a SPARQL endpoint via the ARC2 SPARQL interface.
Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution 3.0 Unported License.