- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Tue, 31 May 2011 19:24:34 +0100
- To: RDB2RDF Working Group WG <public-rdb2rdf-wg@w3.org>
David, On 31 May 2011, at 16:54, RDB2RDF Working Group Issue Tracker wrote: > ISSUE-44 (duplicate quads): Duplicate quads generated by TriplesMaps [R2RML] > > http://www.w3.org/2001/sw/rdb2rdf/track/issues/44 > > Raised by: David McNeil > On product: R2RML > > As far as I can see the R2RML spec does not describe the proper behavior in the case where TriplesMaps produce identical quads. I think a couple of sentences should be added to the spec to specifically say what should happen in this case. Good point. I added at the end of Section 1.4 [1]: [[ RDF graphs cannot contain duplicate triples. Placing multiple equal triples into the same graph has the same effect as placing it into the graph only once. ]] Is this sufficient clarification? Thanks, Richard [1] http://www.w3.org/2001/sw/rdb2rdf/r2rml/#mapping-overview > > My understanding of the correct behavior is: > * R2RML maps are to produce SPARQL RDF datasets. > * SPARQL RDF datasets contain a collection of RDF graphs (many named and one default). > * RDF graphs are sets of triples. > * As "sets", RDF graphs do not contain duplicate triples. > * Therefore SPARQL RDF datasets do not contain duplicate quads. > * Therefore R2RML maps should not produce duplicate quads. > > In particular looking forward to SPARQL 1.1 aggregates I believe this is important to specify. > > Note, SPARQL queries run against the quads produced by an R2RML map can produce duplicate tuples. > > >
Received on Tuesday, 31 May 2011 18:25:04 UTC