- From: Jos de Bruijn <jos.debruijn@gmail.com>
- Date: Thu, 25 Feb 2010 11:19:18 +0100
- To: Axel Polleres <axel.polleres@deri.org>
- CC: RIF <public-rif-wg@w3.org>
Why ## is not in Core: different people had different reasons for not wanting ## in Core. In the end there were fewer people who wanted it than who did not, so it did not get in. Concerning the bug: there is indeed a claim at the start of the appendix that the embedding is in Core, while it is not. I would suggest to include a caveat saying that when operating in Core, the one rule concerning ## should be disregarded. I would find it kind of awkward to have ontology modeling vocabulary (# and ##) in RIF-RDF combinations without tying it in with the RDF ontology modeling vocabulary, even when using only simple entailment. I think this would be awkward for people, especially when querying the RDF entailments. Therefore, I would not favor your proposed solution. Cheers, Jos On 2010-02-25 11:02, Axel Polleres 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 >> > > -- Jos de Bruijn Web: http://www.debruijn.net/ LinkedIn: http://it.linkedin.com/in/josdebruijn Skype: josdebruijn Google Talk: jos.debruijn@gmail.com Mobile phone: +43 660 313 5733
Received on Thursday, 25 February 2010 10:19:09 UTC