- From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
- Date: Mon, 15 Mar 2010 16:08:49 +0100
- To: Jos de Bruijn <jos.debruijn@gmail.com>
- Cc: Ivan Herman <ivan@w3.org>, Chimezie Ogbuji <ogbujic@ccf.org>, SPARQL Working Group WG <public-rdf-dawg@w3.org>, Axel Polleres <axel.polleres@deri.org>, Sandro Hawke <sandro@w3.org>

Sorry, I am a bit late catching up on this. As I understand it, we don't have a problem any more right? What Jos says makes sense to me and I hope that is how RIF works. Otherwise it would be really counterintuitive. Birte On 15 March 2010 08:20, Jos de Bruijn <jos.debruijn@gmail.com> wrote: > 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 >> > -- Dr. Birte Glimm, Room 306 Computing Laboratory Parks Road Oxford OX1 3QD United Kingdom +44 (0)1865 283529

Received on Monday, 15 March 2010 15:17:26 UTC