- From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
- Date: Tue, 24 Aug 2004 17:16:26 +0100
- To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
On Tue, Aug 24, 2004 at 03:02:13 +0100, Dave Beckett wrote: > 2) Source URI in results > > A query may return a Source URI, separate from binding a Source URI > in a matching triple or constraint. > > BRQL Example: > The graph contains aggregated RSS feeds and the query wants to > return all items indicating where they were originally retrieved > from, even with duplicates: > > SELECT ?s WHERE > SOURCE ?s (?x rdf:type rss:item) > > The following could be forbidden, while still allowing the above: > SELECT ?x,?y,?z WHERE > SOURCE <http://www.w3.org/2000/08/w3c-synd/home.rss> (?x ?y ?z) I think this can be dealt with cleanly by having source = NULL (or a single bNode) for all triples in stores with no SOURCE support. So, SOURCE <http://www.w3.org/2000/08/w3c-synd/home.rss> (?x ?y ?z) would be false, SELECT ?s WHERE SOURCE ?s (?x rdf:type rss:item) would return NULL for all triples. Should be easy to implement. - Steve
Received on Tuesday, 24 August 2004 16:16:33 UTC