Efficient, large scale handling of semi-structured data (including RDF) is increasingly an important issue to many web and enterprise information reuse scenarios.
While Lucene has long offered these capabilities, its native capabilities are not intended for large semi-structured document collections (or documents with very different schemas). For this reason we developed SIREn - Semantic Information Retrieval Engine - a Lucene/Solr plugin to overcome these shortcomings and efficiently index and query RDF, as well as any textual document with an arbitrary amount of metadata fields.
SIREn is a Lucene/Solr extension for effificent semi-structured full-text search. SIREn is not a complete application by itself, but rather a code library and API that can easily be used to create a full-featured semi-structured search engine.
SIREn web site: http://siren.sindice.com/
You can download SIREn at: https://github.com/rdelbru/SIREn
Please join the SIREn-User mailing list by subscribing at: http://lists.deri.org/mailman/listinfo/siren