- From: Kjetil Kjernsmo <Kjetil.Kjernsmo@computas.com>
- Date: Thu, 19 Mar 2009 15:55:24 +0100
- To: 'RDF Data Access Working Group' <public-rdf-dawg@w3.org>
All, Our latest application makes extensive use of named graphs, but it has also been the source of much confusion. We haven't documented most of this confusion very well, since we are focused on pragmatic solutions to problems. I hope to document and share more of these problems, as I believe it can be quite nice to have to clarify the spec. I just want to make sure that we're not just being silly before sharing it. :-) There is however, one case that I brought up on the Virtuoso list last year that I feel would be interesting to discuss. The discussion begins with this message (which is part of a longer thread), and the responses to it: http://sourceforge.net/mailarchive/message.php?msg_name=200901051326.51443.Kjetil.Kjernsmo%40computas.com The essence is that we have a default graph which has only triples that state the types of the graphs we have. Then, without knowing the exact graph names (which may be added after the queries are coded into the application), we should be able identify the needed graphs, and then identify the URIs by using ?g a <http://msone.computas.no/graphs/vocab/mediasone#InstanceGraph> . GRAPH ?g { ?uri ms:coverArt <http://ruby3.computas.no/covers/nfi/48739.jpg> . } If I DESCRIBE ?uri, this should give me the triples from the <#InstanceGraph> with ?uri as subject, and they do in this case exist (otherwise the example would be moot). What the linked email shows is that this strategy doesn't work in Virtuoso with DESCRIBE, but it sort of works with CONSTRUCTs (but can't be used in our app since we do not have Feature:LimitByResource). Indeed, I find nothing in the SPARQL 1 spec that would say it should work, but I think it should. :-) I have not identified the concrete problems that would have to be solved for this to work, so I'm just throwing the ball in the hope that someone with a deeper understanding than me will identify those problems. Kind regards Kjetil Kjernsmo -- Senior Knowledge Engineer Mobile: +47 986 48 234 Email: kjetil.kjernsmo@computas.com Web: http://www.computas.com/ | SHARE YOUR KNOWLEDGE | Computas AS PO Box 482, N-1327 Lysaker | Phone:+47 6783 1000 | Fax:+47 6783 1001
Received on Thursday, 19 March 2009 15:00:10 UTC