- From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
- Date: Mon, 8 Feb 2010 15:33:18 +0000
- To: Ivan Herman <ivan@w3.org>
- Cc: Sandro Hawke <sandro@w3.org>, SPARQL Working Group <public-rdf-dawg@w3.org>
>> The general idea, I gather, is to be able to do SPARQL queries against a >> RIF-powered deductive triple store. > > Correct. I do not think this requires more explanation: this is a > succinct description of what the other entailment regime descriptions > aim to achieve... Now that some entailment regimes are defined, I think they give a good example of what needs to be done and how it can be done. >> But I don't understand what needs >> to be spec'd for that; it seems to me like the parts fit together in >> exactly one obvious way. (RIF certainly anticipates this use case; we >> have a Feature At Risk on 1-to-1 lists: rdf:Lists map to RIF lists, but >> do they map back? I hope so, but no one has implemented that yet.) >> > > And I do not expect to be complicated, just one has to have the right > terms... Could all be very easy, it is just hard for me to judge without first getting more into RIF for which I unfortunately don't have much time at the moment. > SPARQL 1.0 had an 'extension point'[1] which means describing what it > means when the basic graph pattern matching is extended to something > more complex. Birte gives a nice description on what should be done > in[2], actually. For the RIF case, one has to specify those conditions > (even if they turn out to be obvious). > > In my understanding, what has to be done is to specify > > 1. A subset of RDF graphs called well-formed for the regime: I believe > that can be any RDF graphs for RIF (here is where the issue with lists > may come in if I understand the problem well) > 2. An entailment relations between well formed graphs which, in the case > of RIF, is probably fully defined by the RIF+RDF semantics, and a > reference might just be fine I tried to not mess with the already defined entailment relations. If RIF defines an entailment relation this might be used as is. > 3. A set of conditions that guarantee that every input yields a finite > set of answers (modulo RDF graph equivalence) > > Due to blank node and such the tricky part is usually #3 and Birte has > come up with some clean conditions on how that can be achieved with > RDF(S) (essentially, blank nodes are skolemized before making the > inferences, ie, only those blank nodes may appear in the answer that > were part of the original graph pattern; I hope Birte will accept my > characterization). Yes that characterises it. > As far as I could see the same approach would work > for RIF as well, mapping these blank nodes to RIF local symbols instead > of skolemization (or after skolemization?) > > Ie, I do not think it is a long editing work but certainly requires > somebody who knows the right references and terminology and also knows > where the possible pitfalls are... I agree. It might all work in the same way as RDF(S), but we better have somebody how knows whether there are additional pitfalls. Birte > I. > > > [1] http://www.w3.org/TR/rdf-sparql-query/#sparqlBGPExtend > [2] http://www.w3.org/TR/2010/WD-sparql11-entailment-20100126/#t13 > >> -- Sandro > > -- > > Ivan Herman, W3C Semantic Web Activity Lead > Home: http://www.w3.org/People/Ivan/ > mobile: +31-641044153 > PGP Key: http://www.ivan-herman.net/pgpkey.html > FOAF : http://www.ivan-herman.net/foaf.rdf > vCard : http://www.ivan-herman.net/HermanIvan.vcf > > -- Dr. Birte Glimm, Room 306 Computing Laboratory Parks Road Oxford OX1 3QD United Kingdom +44 (0)1865 283529
Received on Monday, 8 February 2010 15:33:48 UTC