Hi, has anyone looked into the problem I described on March 7? See below.
Thanks & Regards, Martin Am 07.03.2011 12:09, schrieb Martin Gerlach: > Hi, > > I observed the following SPARQL behavior with Virtuoso Open Source, > Version 06.01.3127, running on Linux version 2.6.27.56-0.1-xen > (geeko@buildhost) (gcc version 4.3.2 [gcc-4_3-branch revision 141291] > (SUSE Linux) ) #1 SMP 2010-12-01 16:57:58 +0100: > > Given the following test graph: > > create graph <http://alx.neofonie.de/test> > > prefix test:<http://alx.neofonie.de/test/> > insert into <http://alx.neofonie.de/test> { > _:b1 a test:Relation . > _:b1 test:agent test:A1 . > _:b1 test:range test:R1 . > _:b2 a test:Relation . > _:b2 test:agent test:A2 . > _:b2 test:range test:R1 . > _:b3 a test:Relation . > _:b3 test:agent test:A2 . > _:b3 test:range test:R2 . > } > > ... the following query: > > prefix test:<http://alx.neofonie.de/test/> > select ?agent ?range > from <http://alx.neofonie.de/test> > where { > _:b a test:Relation . > filter (?agent = test:A1) > optional{ _:b test:agent ?agent.} > optional{ _:b test:range ?range.} > } > > ... returns (as CSV): > > "agent","range" > "http://alx.neofonie.de/test/A1","http://alx.neofonie.de/test/R1"; > "http://alx.neofonie.de/test/A1","http://alx.neofonie.de/test/R1"; > "http://alx.neofonie.de/test/A1","http://alx.neofonie.de/test/R2"; > > ... which contains the wrong (because non existing) result A1/R2. > > Obviously, the filter expression binds ?agent to test:A1 if it is not > bound by the first optional sub query. This can easily be seen by > omitting the filter. > > The question is: Does this behavior conform to the SPARQL spec or is > this a Virtuoso bug? > > This sentence from http://www.w3.org/TR/rdf-sparql-query/ , > section 3, makes me think it is probably a bug: > > "Graph pattern matching produces a solution sequence, where each > solution has a set of bindings of variables to RDF terms. SPARQL FILTERs > restrict solutions to those for which the filter expression evaluates to > TRUE." > > The filter expression, ?agent = test:A1, should not evaluate to TRUE if > ?agent is not bound, and it should also not bind ?agent to test:A1. > > Regards, > Martin > > -- > > (Of course, one can just make the first optional binding a required > binding (result: A1/R1), or move the filter into the first optional > block (result: _/R1, A1/R1, _/R2) to obtain results that make more > sense. The example is a stripped down version of a more complex use case.) > > -- ------------------------------------------------------------------------ *Martin Gerlach* Senior Softwareentwickler Research Neofonie GmbH Robert-Koch-Platz 4 10115 Berlin T +49.30 24627 *413* F +49.30 24627 120 [email protected] http://www.neofonie.de Handelsregister Berlin-Charlottenburg: HRB 67460 Geschäftsführung Thomas Kitlitschko
