- From: Jos de Bruijn <jos.debruijn@gmail.com>
- Date: Mon, 15 Mar 2010 08:20:14 +0100
- To: Ivan Herman <ivan@w3.org>
- Cc: Chimezie Ogbuji <ogbujic@ccf.org>, Birte Glimm <birte.glimm@comlab.ox.ac.uk>, SPARQL Working Group WG <public-rdf-dawg@w3.org>, Axel Polleres <axel.polleres@deri.org>, Sandro Hawke <sandro@w3.org>

Ivan, I can confirm that your basic intuition about the combinations is correct. Chime may not have fully understood the RIF model theory. RIF does not have a minimal model semantics; it has a standard first-order style model theory. Let's consider the empty RIF document R. Since it is empty, there are no constraints on the models, and so every RIF interpretation is a model of R, in particular also every interpretation that satisfies the formula :a#:b. If we now look at combinations of R with the graph S={:a a :b. } we have that only RIF structures I that satisfy :a#:b can be part of common models. Certainly, such structures I satisfy R, and so the combination is satisfiable. Cheers, Jos -- sent from my PDA On 15 Mar 2010, at 06:25, Ivan Herman <ivan@w3.org> wrote: > > > On 2010-3-15 01:48 , Chimezie Ogbuji wrote: >> Ivan, >> >> On 3/13/10 5:19 AM, "Ivan Herman" <ivan@w3.org> wrote: >>> Chime, >>> I do not understand... >> >> Okay, I'll see if I can help with that. I've sent Jos a separate >> email >> about this as well. >> >>> On 2010-3-12 21:10 , Chimezie Ogbuji wrote: >> ..snip.. >>> My understanding of the proposed semantics (by Axel) for >>> rif:imports is >>> that this combination is transformed as follows: >>> >>> 1. Starting point >>> G: _:a rdf:type _:b . >>> <> rif:imports <R> . >>> R: empty >>> >>> 2. Apply the semantics >>> G': _:a rdf:type _:b >>> R': Import(G, <http://www.w3.org/2007/rif-import-profile#Simple>) >>> >>> (whether the <> rif:imports <R> is removed from G is still an open >>> question but does not seem to influence this issue) >> >> Okay, but independent of how rif:imports is interpreted (for a lack >> of a >> better word), the SG still only has one triple relevant to RIF-simple >> entailment, right?: >> >> _:a rdf:type _:b >> >>> 3. From the RIF point of view, that is equivalent to: >>> R'' : _a # _b . >>> >>> (using RIF's unique id-s which look very much like skolemization >>> to me). >> >> Okay, this is the point where the issue comes in. I'm not sure >> what you >> mean by 'from the RIF point of view', because - as I understand it - >> entailment does not involve any RIF interpretation of the RDF graph >> (which >> is the reason why we need to embed the triples from the scoping >> graph into >> the RIF document in order to interpret them using RIF semantics). >> > > This is the crucial point and I think you did the best thing by asking > Jos on this, and there might indeed be a terminological/editorial > issue > in the RIF-RDF document (and it is the right time to signal this if > there is!). > > My mental model of the RIF-RDF combination has always been that when a > RIF rule set 'imports' an RDF graph, than this means as if all triples > were effectively defined in terms as RIF frames. Ie, the import will > definitely create the following: > > _a[rdf:type->_b] > > furthermore, the definition of the common interpretation with the 10 > rules puts an extra set of correspondence on how to 'see' the RDF > triples through a RIF glass. Ie, in my mind, that means that the RIF > entailment part operates on the single rule > > _a # _b . > > If true, this means that your issue below becomes moot. If false, > than I > am not sure any more how this common thing works... > > So Jos, you are the source of all wisdom! > > Ivan > > > >> So, at this point (i.e., before 3 above) we form the following >> combination: >> >> <Rempty,G''> >> >> Where G'' is sk(G'): >> >> <unique-URI-1> rdf:type <unique-URI-2> (lets refer to this triple >> as t1) >> >> The problem is that there is no (simple) interpretation for G'' in >> which >> IEXT(IS(rdf:type)) is empty. Since, G'' is ground, we know I(t1) >> is true >> and that IEXT(IS(rdf:type)) must not be empty (from what tr/rdf-mt >> says >> about how simple entailment interprets ground RDF graphs in 1.4). >> >> Since Rempty is empty, I_truth(I_isa(a,b))= false, and by the >> wording of >> condition 7, IEXT(IS(rdf:type)) must be empty. However, above we >> see that >> it can't be empty. >> >>> Do I severely miss something here? >>> Actually, if what you say was true, then I think there is a >>> problem in >>> the RIF-RDF document. That has to be signalled to the RIF group >> >> I'm not sure if this necessarily indicates a problem with the RIF-RDF >> document (hopefully Jos can speak on this) but perhaps suggests >> that the >> embeddings (or at least some of them: Simple and RDF for example) >> should be >> made normative since implementations cannot practically implement >> RIF-RDF >> entailment without them. Or at least, a simple paragraph >> emphasizing the >> counter-intuitive behavior of combinations where there is not >> already a >> correspondence between triples, frames, and their terms. >> >> -- Chime >> >> >> =================================== >> >> P Please consider the environment before printing this e-mail >> >> Cleveland Clinic is ranked one of the top hospitals >> in America by U.S.News & World Report (2009). >> Visit us online at http://www.clevelandclinic.org for >> a complete listing of our services, staff and >> locations. >> >> >> Confidentiality Note: This message is intended for use >> only by the individual or entity to which it is addressed >> and may contain information that is privileged, >> confidential, and exempt from disclosure under applicable >> law. If the reader of this message is not the intended >> recipient or the employee or agent responsible for >> delivering the message to the intended recipient, you are >> hereby notified that any dissemination, distribution or >> copying of this communication is strictly prohibited. If >> you have received this communication in error, please >> contact the sender immediately and destroy the material in >> its entirety, whether electronic or hard copy. Thank you. >> > > -- > > 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 >

Received on Monday, 15 March 2010 08:26:37 UTC