- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Tue, 4 Oct 2011 10:05:30 +0100
- To: Axel Polleres <axel.polleres@deri.org>
- Cc: SPARQL Comments <public-rdf-dawg-comments@w3.org>
Hi Axel, On 4 Oct 2011, at 06:05, Axel Polleres wrote: >>>> An RDF Dataset comprises one graph, the default graph, which does not >>>> have a name, and zero or more named graphs, where each named graph is >>>> identified by an IRI. >> >> You are right. If taken literally, this definition [1] implies that an RDF Dataset can't have the same triples in the default graph and in a named graph. This clearly isn't the intention, so the wording is a bug in the SPARQL spec and needs to be fixed. > > I don't see how the wording at [1] would imply disjointness of the named and default graphs. > Since a *named graph* is a *pair* of a graph and its name (as indeed made more explicit in [2]), > any named graph is per definition different from the default graph or from any other named graph, so > I don't think that the wording at [1] is buggy. If there's a named graph <u1,G1>, then it is reasonable to say that G1 has the name u1, because G1 is paired with a graph name u1. If one accepts G1 has the name u1 as a true statement, then it follows that G1 cannot be the default graph, because [1] states that [the default graph] does not have a name. I agree that [2] is unambiguous. The problem is that [1] can be easily read as implying something that isn't true according to [2], as has happened here in RDF-WG. Best, Richard > > best regards, > Axel > > > On 30 Sep 2011, at 11:28, Richard Cyganiak wrote: > >> Hi pa, >> >> (cc SPARQL comments list) >> >> On 29 Sep 2011, at 16:57, Pierre-Antoine Champin wrote: >>> I realize that a statement that I made: >>> >>> On 09/29/2011 04:42 PM, Pierre-Antoine Champin wrote: >>>> I know that SPARQL does not require that the default graph is *also* >>>> present as a named graph (though it does not forbid it) >>> >>> could be argued against by the way SPARQL defines a dataset: >>> >>>> An RDF Dataset comprises one graph, the default graph, which does not >>>> have a name, and zero or more named graphs, where each named graph is >>>> identified by an IRI. >> >> You are right. If taken literally, this definition [1] implies that an RDF Dataset can't have the same triples in the default graph and in a named graph. This clearly isn't the intention, so the wording is a bug in the SPARQL spec and needs to be fixed. >> >> The formal definition [2] is fine. >> >> (RDF graphs are set of triples. If two graphs contain the same triples, they are the same graph they have no identity beyond the triples they contain.) >> >> Best, >> Richard >> >> [1] http://www.w3.org/TR/sparql11-query/#rdfDataset >> [2] http://www.w3.org/TR/sparql11-query/#sparqlDataset >> >
Received on Tuesday, 4 October 2011 09:06:12 UTC