On 26 Nov 2010, at 17:47, Christian Brenninkmeijer wrote: > On 26/11/2010 17:17, Richard Cyganiak wrote: >> That being said: Having two d2rq:Databases in a single mapping file >> isn't really supported by the D2RQ SPARQL-to-SQL engine. It may or >> may >> not work, depending on rather random factors. But still, the choice >> of >> expansion for the "map:" prefix shouldn't affect the generated query. >> > I noticed that too. > I (a complete D2R novie) think it looks like the engine tries to pick > which database to query. > if it can find anything in the query to point to one of the > databases it > stops looking and just queries that one. > For example if you reference for a type only in one database. > > Only queries where there is no way for the optimizer to pick a > database > appear to work on multiple databases at the same time.
I think that's an accurate description of what's going on. The rewriting engine is not designed to work with multiple DBs, so sometimes it works by accident, but in general it won't. > Is this something you are thinking of supporting in the Future. It would certainly be great if D2RQ had that ability. It's an open source project and contributions are always welcome ... > I ended up moving to Jena because of it. Not sure what that means -- D2RQ uses Jena as well. Anyways, if you want to integrate several data stores, at this point I'd recommend either using the basic federated query feature of Andy Seaborne's ARQ, or Extract-Transfer-Load them all into one triple store. Best, Richard > > Regards > Dr Christian Brenninkmeijer > University of Manchester > > ------------------------------------------------------------------------------ > Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! > Tap into the largest installed PC base & get more eyes on your game by > optimizing for Intel(R) Graphics Technology. Get started today with > the > Intel(R) Software Partner Program. Five $500 cash prizes are up for > grabs. > http://p.sf.net/sfu/intelisp-dev2dev > _______________________________________________ > d2rq-map-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/d2rq-map-devel ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ d2rq-map-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/d2rq-map-devel
