I remember some discussions a while back about one of the barriers to implementing GeoSPARQL in Jena being the lack of a good indexing library to use
I notice that Lucene 4.0 has a new Spatial module - http://lucene.apache.org/core/4_0_0-BETA/spatial/index.html – which is itself built on another library Spatial4j which is ASL licensed Would these be sufficient pieces to get us started? I haven't looked in detail as to whether these libraries provide the specific geospatial primitives and functions we'd need to implement GeoSPARQL Rob
