- From: Jos de Bruijn <debruijn@inf.unibz.it>
- Date: Wed, 24 Feb 2010 12:38:38 +0100
- To: Axel Polleres <axel.polleres@deri.org>
- CC: Sandro Hawke <sandro@w3.org>, Birte Glimm <birte.glimm@comlab.ox.ac.uk>, SPARQL Working Group <public-rdf-dawg@w3.org>
>> On 2010-02-24 12:24, Axel Polleres wrote: >>> Below I forward some thought from jos on this with his consent: >>> >>> @jos: can you ealborate what exactly you mean here: >>> >>>> 2- the RDF(S) semantics gives you more than just blank nodes. >>> >>> in how far is this a (potential) problem? >> >> I'm not saying this is a problem per se. You were simply not taking the >> RDF(S) semantics (i.e., axiomatic triples & semantics conditions) into >> account in the definition you proposed. > > yes, this is another issue. good point. > >> Of course one needs to be careful with the infinite axiomatic triples, >> especially when considering query answering and not just checking >> entailment. > > A common way to deal with this in a finite approximation way is > a) ignoring (specifically the infinite) axiomatic triples alltogether > b) take only those from the infinite axiomatic triples (those about container membership properties) > that appear in the graph... I believe the latter is what we do in the current RDF(S) entailment regime, yes Birte? b) seems to be the most reasonable way to go; but make sure to include at least one representative (for queries with blank nodes). Unnecessarily ignoring parts of the semantics (as in a) seems rather a bad idea. Cheers, Jos > > Axel > >> >> >> Jos >> >>> >>> Axel >>> >>> >>>> ============================================================================ >>>> On 2010-02-24 12:07, Axel Polleres wrote: >>>>> >>>>> On 24 Feb 2010, at 11:04, Jos de Bruijn wrote: >>>>>> On 2010-02-24 11:28, Axel Polleres wrote: >>>>>>> Hi Jos, >>>>>>> >>>>>>> Can you check this briefly and tell me whether I don't oversimplify >>>>>>> things here? >>>>>> >>>>>> I will have a more detailed look at it later on, but a few first comments: >>>>>> - you do not consider equality between data values, e.g. >>>>>> "1"^^int="1"^^decimal >>>>> >>>>> hmmm, I am at the moment, not sure how far this is a problem, but I definitly should include this in the issues! >>>>> >>>>> >>>>>> - I did not see how a minimal model for RIF-RDF combinations is defined, >>>>>> in particular I see no blank nodes or RDF(S) semantics >>>>> >>>>> ? Can't we just treat them as skolem constants? We are just interested in query answering... >>>> >>>> 1- if you treat blank nodes as skolem constants you need to say so. >>>> 2- the RDF(S) semantics gives you more than just blank nodes. >>>> >>>>> if you agree, I forward your comments to SPARQL, ok? >>>> >>>> Sure. >>>> >>>> >>>> Jos >>> >>> >> >> -- >> Jos de Bruijn >> Web: http://www.debruijn.net/ >> Phone: +39 0471 016224 >> Fax: +39 0471 016009 >> > -- Jos de Bruijn Web: http://www.debruijn.net/ Phone: +39 0471 016224 Fax: +39 0471 016009
Received on Wednesday, 24 February 2010 11:38:27 UTC