Hi Silvia, This looks like a bug in D2RQ. But I'm not sure why you're writing the query like that. I think if you just replace ?a with ?z, and drop the FILTER, you should get the desired result.
Best, Richard On 13 Apr 2011, at 17:30, Silvia Stefanova wrote: > Dear Richard, > > My name is Silvia Stefanova. I am a Ph.D student at Uppsala Database > Laboratory (UDBL) at the Department of Information Technology, Uppsala > University, Sweden. My PhD project is on long-term preservation of > scientific data using Semantic Web representations. > > I am writing to you since I would like to ask you for some help with D2RQ. > I am running D2RQ by Jena and use the Berlin's relational data. The mapping > is as here > http://www4.wiwiss.fu-berlin.de/bizer/BerlinSPARQLBenchmark/results/store_config_files/d2r-mapping.n3. > I am trying to run Query 9 (the SPARQL DESCRIBE query) from the Berlin > benchmark as a a SELECT query. Since I want to receive the result as RDF > triples I define the query like this: > > SELECT ?x ?y ?z > WHERE { > {<http://www4.wiwiss.fu-berlin.de/bizer/bsbm/v01/instances/dataFromRatingSite1/Review6712> > rev:reviewer ?x . > ?x ?y ?z.} > UNION > > {<http://www4.wiwiss.fu-berlin.de/bizer/bsbm/v01/instances/dataFromRatingSite1/Review6712> > rev:reviewer ?a. > ?x ?y ?z. > FILTER(?z = ?a).} } > > whose result should correspond to the result from the Berlin Query 9 (this I > can run) > > The problem is that I get from Java the following exception > > "de.fuberlin.wiwiss.d2rq.nodes.FixedNodeMaker cannot be cast to > de.fuberlin.wiwiss.d2rq.nodes.TypedNodeMaker". > > It looks like it is not allowed to change places of variables, this what the > filter is doing. Or ... ? Is this the reason for that exception? Can I do > anything in order to run this query with D2RQ? > > I am looking forward hearing from you! > > Best Regards, > Silvia > > ------------------------------------------------------------------------------ Benefiting from Server Virtualization: Beyond Initial Workload Consolidation -- Increasing the use of server virtualization is a top priority.Virtualization can reduce costs, simplify management, and improve application availability and disaster protection. Learn more about boosting the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev _______________________________________________ d2rq-map-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/d2rq-map-devel
