- From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
- Date: Fri, 1 Oct 2004 19:21:40 +0100
- To: DAWG public list <public-rdf-dawg@w3.org>
On Fri, Oct 01, 2004 at 01:22:24 -0400, Kendall Clark wrote: > > On Fri, Oct 01, 2004 at 06:17:16PM +0100, Steve Harris wrote: > > > conjunctive ones, but it explodes the number of queries needed > > dramatically. > > In cases where the implementation strategy is based on RDBMS/SQL or in > every case? I genuinely don't know. In every case - the algorithm prduces a number of prurely conjunctive expressions from a mixed dis/con-juntive one. There may well be simple omptisation strategys that mean you dont have to do the full naive expansion, but I have no idea. > > In any case, I'm not convinced that users generally think in terms of > > graph level disjunction, as I said I've not had requests for it. > > IIRC, Network Inference gets this a lot from its users and that's how > 2.13 ended up in UC&R. > > > SQL has > > no equivalent syntaxic form to graph disjunction > > Hmm, well, that's of only limited applicability here, IMO. But YYMV > and clearly does. :> :) I agree its a weak point, I just threw it in to show that theres precident for not supporting disjuntive graph expressions. > > > We have 2.13 and 3.13 in UC&R that imply disjunction in SPARQL. I > > > haven't heard enough to disregard that. > > > > 2.13 can be answered just as well with []'s, and 2.13 is the justification > > for 3.13. > > Well, as you say, we don't have a proof that optionals can satisfy > 2.13 in every case. We do have evidence that doing so in common cases > puts a pretty high burden on users. Some of those > disjunction-via-optional examples are a bit hairy. I can't imagine > ordinary folks writing them. Bear in mind that those are the /exact/ translations, the optional expression users really write are the natural ones and dont have the hairy disjuntive value constraints. > Anyway, I've said my piece about this. Thanks for the response. Thank you for raising the points. I certainly agree with you that none of the points on thier own are reason enough to drop disjunction, but together I think they make a good argument. - Steve
Received on Friday, 1 October 2004 18:21:47 UTC