he LUPOSDATE SPARQL system supports various approaches to manage RDF data and process SPARQL queries: Index, RDF3X, Stream, Jena and Sesame. Jena [21] and Sesame [3] refer to third-party SPARQL engines. Index is our in-memory Engine presented in [6]. Stream is our stream-based implementation (see [10]). RDF3X is a re-implementation of [14], but is further enhanced with additional optimization strategies.
Queries with joins, however, are more likely to have coincident attribute names and require explicit differentiation. For example, the primary key of both Addresses and Orders is called id. Qualifying all the field names
P. Haase, J. Broekstra, A. Eberhart, and R. Volz. The Semantic Web - ISWC 2004. Proceedings of the Third
International Semantic Web Conference, volume 3298 of Lecture Notes in Computer Science, Hiroshima, Japan, Springer-Verlag, (2004)
J. Broekstra, A. Kampman, and F. van Harmelen. Proceedings of the first International Semantic Web
Conference (ISWC 2002), 2342, page 54--68. Sardinia, Italy, Springer Verlag, Heidelberg Germany, (June 2002)See also http://www.openrdf.org/.