good afternoon; On 11 Jul 2014, at 10:38, Carsten Keßler <m...@carsten.io> wrote:
> Dear all, > > I'm running Virtuoso OS 7.1.0 and trying to run some federated queries to > DBpedia and Europeana. Here's an example of what I'm trying to do (fetch some > Europeana artifacts created during the lifetime of Ghandi, as a simplified > example): > > prefix db: <http://dbpedia.org/ontology/> > prefix dc: <http://purl.org/dc/elements/1.1/> > prefix xsd: <http://www.w3.org/2001/XMLSchema#> > > SELECT * WHERE { > > SERVICE <http://dbpedia.org/sparql> { > <http://dbpedia.org/resource/Mahatma_Gandhi> db:birthDate > ?birth ; > db:deathDate ?death . > > } > > SERVICE <http://europeana.ontotext.com/sparql> { > SELECT * WHERE { > ?artifact dc:date ?date . > FILTER ( ?date >= xsd:string(?birth) && ?date <= > xsd:string(?death) ) > } LIMIT 10 > } > > } LIMIT 10 > > If I run this through the sparql.org endpoint, it works without problems [1]. > Virtuoso gives me the following error, though: > > Virtuoso 37000 Error SP031: SPARQL compiler: Variable 'birth' is used in the > query result set but not assigned > Is this a know limitation of Virtuoso? > > Thanks, > Carsten Notwithstanding the sparql.org response, the description of variable scope[1] provides no binding for either ?birth or ?death, which lends support to virtuoso’s compiler. See, for example, the ‘minus’ example[2]. One might argue that the discussion in the federation spec[3] would lead one to believe that the sparql.org behavior is a reasonable extension. I would agree, but nothing in the federation semantics requires it. best regards, from berlin, ----- [1] http://www.w3.org/TR/sparql11-query/#variableScope [2] http://www.w3.org/TR/sparql11-query/#idp899488 [3| http://www.w3.org/TR/sparql11-federated-query/#values ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Virtuoso-users mailing list Virtuoso-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/virtuoso-users
