Here is a short overview and comparison of RDF querying with SPARQL and Jena which is presented as follows: 1. SPARQL; 2. SPARQL from inside Jena; 3. Explicit and implicit relations when querying with Jena 4.Querying remote SPARQL endpoitns
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/.
J. Carroll, C. Bizer, P. Hayes, and P. Stickler. WWW '05: Proceedings of the 14th international conference on World Wide Web, page 613--622. New York, NY, USA, ACM, (2005)
K. Cheung, H. Frost, M. Marshall, E. Prud'hommeaux, M. Samwald, J. Zhao, and A. Paschke. BMC Bioinformatics, (2009)"We have explored a tool called "FeDeRate", which enables a global SPARQL query to be decomposed into subqueries against the remote databases offering either SPARQL or SQL query interfaces.".
K. Cheung, H. Frost, M. Marshall, E. Prud'hommeaux, M. Samwald, J. Zhao, and A. Paschke. BMC Bioinformatics, (2009)"We have explored a tool called "FeDeRate", which enables a global SPARQL query to be decomposed into subqueries against the remote databases offering either SPARQL or SQL query interfaces.".