- From: Antoine Isaac <aisaac@few.vu.nl>
- Date: Tue, 24 Mar 2009 11:51:58 +0100
- To: Alistair Miles <alistair.miles@zoo.ox.ac.uk>
- CC: SWD WG <public-swd-wg@w3.org>
Hi Alistair, Interesting comments, thanks! I guess that though in many cases the outcome of the two options would be the same, the formal semantics are completely different ;-) One question though: should "GRAPH" really replace "FROM NAMED", or just be added to the existing queries? Antoine > Hi Antoine, > > Sorry for not responding sooner on this, for the most part it looks > fine, however I would change the SPARQL queries to use the GRAPH > keyword instead of FROM NAMED, see below. > > On Sun, Dec 14, 2008 at 08:09:02PM +0100, Antoine Isaac wrote: >> Hi everyone, >> >> About the following action: >> >>> [PENDING] ACTION: Antoine propose 1 or 2 SPARQL examples showing >>> named graph usage [recorded in >>> [36]http://www.w3.org/2008/11/25-swd-minutes.html#action14] >> I'd like to propose to add to the Primer the sub-section below (it would be at the very end of the Primer). >> I hope this capture the spirit of our resolution for ISSUE-36 [1] appropriately, while not going too much in the direction of not yet stabilized practices. >> >> Feedback of the WG is highly welcome! >> >> Cheers, >> >> Antoine >> >> [1] http://www.w3.org/2006/07/SWD/track/issues/36 >> >> =============== >> >> 5.3 SKOS, RDF Datasets and Information Containment >> >> In a context of networked KOSs, some applications may require tracking >> provenance or ownership of SKOS statements, for instance for trust >> purposes. A specific issue is how to establish explicit links between a >> concept scheme and every piece of information that is stated in the >> original KOS it represents, including for instance semantic relationships >> between concepts. >> >> Such functionality, albeit identified as a candidate requirement [SKOS-UCR], is currently outside the scope of SKOS. In RDF, statements comes as context-free triples, which makes it difficult to represent containment and provenance. >> >> However, solutions for such problems have been proposed, like named graphs [NAMED-GRAPHS], and the use of RDF Datasets in SPARQL [SPARQL]. A SKOS concept scheme can be related to an RDF Dataset, or even asserted to be such a Dataset, which enables to create SPARQL queries dealing with some form of provenance/containment. Continuing the example of Section 3.2, and assuming that ex1:referenceAnimalScheme and ex2:catScheme have been managed as appropriate RDF Datasets (here, named graphs), the query >> >> SELECT ?x ?y >> FROM NAMED <ex2:catScheme> >> WHERE { ?x skos:broader ?y } > > SELECT ?x ?y > WHERE { > GRAPH ex2:catScheme { > ?x skos:broader ?y > } > } > >> may return (ex2:abyssinian, ex1:cat) as a result, while this tuple would >> not appear among the results of >> >> SELECT ?x ?y >> FROM NAMED <ex1:referenceAnimalScheme> >> WHERE { ?x skos:broader ?y } > > SELECT ?x ?y > WHERE { > GRAPH ex1:referenceAnimalScheme { > ?x skos:broader ?y > } > } > >> Readers should nevertheless be aware that these mechanisms have not been widely used at the time of writing, and that different standard practices could emerge in the future. >> >> >
Received on Tuesday, 24 March 2009 10:52:32 UTC