- From: Michael Kifer <kifer@cs.sunysb.edu>
- Date: Thu, 25 Feb 2010 05:20:17 -0500
- To: Axel Polleres <axel.polleres@deri.org>
- Cc: RIF <public-rif-wg@w3.org>
I believe that the PRD group (or some subset of it) felt that it complicates the life for PRD. michael On Thu, 25 Feb 2010 10:02:09 +0000 Axel Polleres <axel.polleres@deri.org> wrote: > Hi all, > > Ivan raised the question why ## was not in RIF Core... I tried to exploit my memories on this as good as I can, but I am not 100% sure whether I got everything right and would seek confirmation of the group. Also, there's a small issue which I don't like and want to raise here... > > > since from the mails below, the thread may be hard to grasp, let me summarise: > > Ivan asked for the reason of the absence of ## in RIF Core - in the context of modelling rdfs:subclassOf . > I didn't really remember precisely the details why we dropped ## from Core, but pointed Ivan to the difference > between ## and rdfs:subclassOf , that is, ## not being reflexive. > > However, what then still worried me a bit is following: > Note that http://www.w3.org/TR/rif-rdf-owl/ restricts RDF-OWL interpretations > in such a way that ## implies rdfs:subclass but not the other way around. > The Embedding of RIF combinations in Section 9.1.3 of > http://www.w3.org/TR/rif-rdf-owl/ enforces this by a rule... which then makes even the > embedding of simple RDF entailment go outside RIF Core... I am not sure whether I like this. :-| > > Ivan, suspected even a "bug" here, by the assumption that if I talk about simple and RDF interpretations, > I shouldn't worry about the RDFS vocabulary, but I wouldn't go that far: > > As far as I can see, this is not problematic. We just restrict that when you throw RIF and RDF stuff together, > a link is made from ## to rdf:subclasss... that implies that anything which is stated as ## in RIF is > exported to rdfs:subclassOf (but NOT the other way around!) only in RIF-RDFS-entailment this would have > cross-effects (since RDFS interpretations imply reflexivity on rdfs:subclass), but not in RIF-Simple and RIF-RDF. > > Still, and here I think Ivan's concern plays a role, I don't like that now for embedding simple > RDF or RDF in RIF, I need non-core rules... in fact, it seems to me that the rule > in Section 9.1.3 of http://www.w3.org/TR/rif-rdf-owl/ > > Forall ?x ?y (?x[rdfs:subClassOf -> ?y] :- ?x ## ?y]) )) > > is irrelevant for Simple and RDF entailments. Particularly, this is the case as long as the RIF ruleset in the combination does not use ##. > Can you confirm this? > > If I had a wishlist, I would opt for moving the semantic condition on > > "7. IEXT(IS(rdfs:subClassOf)) is a superset of the set of all pairs (a, b) in Dind x Dind such that Itruth(Isub(a,b))=t;" > > to just apply for RIF-RDFS-models "upwards" > > Can we still change this? > > Axel > > > Begin forwarded message: > > > From: "Ivan Herman" <ivan@w3.org> > > Date: 25 February 2010 09:46:04 GMT > > To: "Polleres, Axel" <axel.polleres@deri.org> > > Cc: "Sandro Hawke" <sandro@w3.org> > > Subject: Re: A technical RIF question > > > > > > > > On 2010-2-25 10:10 , Axel Polleres wrote: > >> > >> On 25 Feb 2010, at 09:03, Ivan Herman wrote: > >> > >>> > >>> On Feb 25, 2010, at 09:56 , Axel Polleres wrote: > >>> > >>>> Phew, IIRC this has some historic reasons, which I don't really remember. > >>>> > >>>> Firstly, ## is not the same as rdfs:subclass (e.g. ## is NOT reflexive, IIRC) > >>>> > >>>> The simple solution is, similar to what I answered to Dan on owl:sameAs: > >>>> > >>>> just use rdfs:subclass in your rules and don't bother about ## they are not the same thing... > >>>> > >>> > >>> Well, o.k. I will try to avoid referring to ## in my tutorial part then...:-( > >>> > >>>> What worries me a bit more: > >>>> Note that http://www.w3.org/TR/rif-rdf-owl/ restricts RDF-OWL interpretations > >>>> in such a way that ## implies rdfs:subclass but not the other way around. > >>>> The Embedding of RIF combinations in Section 9.1.3 of > >>>> http://www.w3.org/TR/rif-rdf-owl/ enforces this by a rule... which then makes even the > >>>> embedding of simple RDF entailment go outside RIF Core... I am not sure whether I like this. :-| > >>>> > >>> > >>> Oops. But isn't this a bug? If I talk about an RDF interpretation, than the RDFS vocabulary is immaterial. and subClassOf is in the RDFS vocabulary and _not_ in the RDF vocabulary! > >> > >> As far as I can see, this is not problematic. We just restrict that when you throw RIF and RDF stuff together, > >> a link is made from ## to rdf:subclasss... that implies that anything which is stated as ## in RIF is exportet to rdfs:subclassOf (but NOT the other way around!) > >> only in RIF-RDFS-entailment this would have cross-effects (since RDFS interpretations imply reflexivity on rdfs:subclass), but not in RIF-Simple and RIF-RDF > >> > >> If you agree, I should carry this discussion to the RIF group... > >> > > > > Sure > > > > Ivan > > > > > >> HTH, > >> Axel > >> > >> > >>> > >>> I think this is a bug that you should report before this goes to PR:-( > >>> > >>> Ivan > >>> > >>> > >>>> I am not really swapped in on that at the moment, and for more details and clarifications, > >>>> I'd prefer to get back to the group... > >>>> > >>>> Axel > >>>> > >>>> On 25 Feb 2010, at 08:22, Ivan Herman wrote: > >>>> > >>>>> (background: I try to update my tutorial slide set...) > >>>>> > >>>>> Question: what is the background of the fact that '#' is defined for > >>>>> Core and '##' is not? > >>>>> > >>>>> For many RDF users I would think Core (or maybe strongly safe Core) > >>>>> would be the natural rule set to use in the sense that would cover most > >>>>> of their needs (at least I believe). The fact of having '#' is fine, it > >>>>> is the equivalent of rdf:type. But, for RDFS users, so to say, suddenly > >>>>> there is this gap of '##'; either they have to keep to Core and use > >>>>> explicitly rdfs:subClassOf, or they use '##', thereby getting into BLD... > >>>>> > >>>>> So: what is the technical reason for this? > >>>>> > >>>>> Thanks > >>>>> > >>>>> Ivan > >>>>> -- > >>>>> > >>>>> 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 > >>>>> > >>>> > >>> > >>> > >>> ---- > >>> 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 > >>> > >>> > >>> > >>> > >>> > >> > > > > -- > > > > 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 Thursday, 25 February 2010 10:20:47 UTC