- From: Axel Polleres <axel.polleres@deri.org>
- Date: Thu, 13 Dec 2007 15:24:21 +0100
- To: Chris Welty <cawelty@gmail.com>
- CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
Chris Welty wrote: > > > </chair> > > Back in August I proposed a "friendly amendment" for the rif:subClassOf > relation (aka ##) saying that: > > rif:subClassOf rdfs:subproperty rdfs:subClassOf . that would mean that each rif:subClassOf should be a rdf:subClassOf... aehm... shouldn't it be - if any - just the other way around? rdfs:subClassOf is more specific. Axel > Michael was not opposed, he thought that it was obvious. Jos replied as > below, indicating some possible softness on the point. I don't think > DaveR responded. But I didn't push on it as some other thing must have > come up (like vacation probably), and the thread ended with Jos' message > below. > > So before we give up on it, because I do think it would be useful to > have in BLD, I'd like to see if this will make a difference to anyone, > specifically the objectors to having rif:subClassOf (DaveR, Jos, ?). > > -Chris > > <chair> > > Jos de Bruijn wrote: >> <snip/> >> >>>> rif:subclassOf is not a new concept. It is there in >>>> every standard OO language. Jos' arg was that it is a new word in the >>>> vocabulary, and Dave was questioning whether RIF should define such a >>>> concept (incl. rdfs:subclassOf) in the first place. >>> I'm just hoping it makes what you proposed a little more palatable. But >>> let's see - Dave and Jos? Does Michael need still more coffee or do I? >> >> My argument was that there are already semantic Web languages for >> defining ontologies (including the subclass relation), so that RIF >> should probably not invent a new vocabulary for defining ontologies (or >> classifications), but rather show how existing vocabularies for ontology >> definition (including (subsets of) RDFS) can be combined with the RIF. >> >> Chris' proposal (rif:subclass rdfs:subproperty rdfs:subclass; use >> rdf:type for instance statements?) seems to extend the RDFS vocabulary, >> rather than creating a new vocabulary. >> This could be a possible way to go for exchanging data models which do >> not have reflexive subclass statements; however, I am not 100% convinced >> that we need this extension. >> >> I guess an important question is really whether people want to use >> several different data models in the same RIF rule set. >> >> >> Best, Jos >> >> >>> -Chris >>> >>>>> Intuitively, it seemed to me that every rif:subclass relation is an >>>>> rdfs:subclass relation, but there may be rdfs:subclass relations that >>>>> a translator will not want to consider as rif:subclass (e.g. the >>>>> reflexive cases, the cases where one of the arguments is not a class, >>>>> the case where one of the arguments is a piece of rdf or rif syntax, >>>>> etc). >>>>> >>>>> I guess it depends on whether you want every rdfs:subclass relation >>>>> (including the entailed ones) in rdf graphs to entail rif:subclass in >>>>> RIF rules or whether you want a translator to do it. I could go >>>>> either way. >>>>> >>>>> Note that rif:subclass rdfs:subproperty rdfs:subclass does not make >>>>> rif:subclass reflexive - it does mean that for every A rif:subclass B >>>>> we would also have A rdfs:subclass A and B rdfs:subclass B, but >>>>> that's just what rdfs:subclass means. Shouldn't be a problem for >>>>> rif:subclass. >>>>> >>>>> <chair> >>>>> >>>>>> --michael >>>>>>> </chair> >>>>>>> Here is a hopefully friendly amendment to the proposal to add a >>>>>>> rif:subClassOf relation to BLD: >>>>>>> >>>>>>> If we just say that <rif:subClassOf rdfs:subPropertyOf >>>>>>> rdfs:subClassOf> I think it goes part of the way in addressing the >>>>>>> chief concern of Jos and Dave (which is, as I understand it, that >>>>>>> we shouldn't add yet another subclass relation to the semantic web). >>>>>>> >>>>>>> This would make it clear that we are not really creating something >>>>>>> new, just imposing a restriction on something already there - in >>>>>>> particular all rif:subClassOf relations are also rdfs:subClassOf >>>>>>> relations, but not the reverse, and we would say that >>>>>>> rif:subClassOf is not reflexive, only holds between classes, etc. >>>>>>> >>>>>>> Less the new name, this is what Jos proposed - to define a suitably >>>>>>> restricted subset of RDFS that would be usable for RIF. I think >>>>>>> the new name (rif:subClassOf) helps to make it clear that we do not >>>>>>> intend the full rdfs semantics, rather than "hiding" that in the >>>>>>> semantics. >>>>>>> >>>>>>> <chair> >>>>>>> >>>>>>> -Chris >>>>>>> >>>>>>> Chris Welty wrote: >>>>>>>> Michael Kifer wrote: >>>>>>>>> Rumblings on why we need classification terms in RIF >>>>>>>>> (and why RDF's vocab should not be used) >>>>>>>>> =================================================== >>>>>>>>> >>>>>>>>> Two issues: whether we should define facilities for expressing >>>>>>>>> some data >>>>>>>>> model stuff and whether we should use rdfs for this. >>>>>>>>> >>>>>>>>> Rationale: >>>>>>>>> If we do not have such constructs then everybody will be >>>>>>>>> inventing their >>>>>>>>> own. People will not be able to specify any part of their data >>>>>>>>> model in RIF >>>>>>>>> which will reduce the usefulness of RIF as an exchange >>>>>>>>> language. >>>>>>>>> >>>>>>>>> Why it is not good to use RDF's facilities to define class >>>>>>>>> hierarchies.: >>>>>>>>> RDF is a foreign language whose semantics is burdened with >>>>>>>>> non-standard >>>>>>>>> things. For instance, subclass is reflexive. >>>>>>>>> >>>>>>>>> This is bad because not every language out there uses >>>>>>>>> reflexive subclasses. >>>>>>>>> For instance, if we map, say, FLORA-2's subclass relationship >>>>>>>>> to RDFS's then >>>>>>>>> in the translation (RIF) the query whether foo is a subclass >>>>>>>>> of foo will >>>>>>>>> say "yes" but in FLORA-2 it will say "no". >>>>>>>> </chair> >>>>>>>> No, no - translating flora2:subclass into rdfs:subclass would be >>>>>>>> incorrect, because they have different semantics. For me, this is >>>>>>>> the stronger point in favor of rif:subclass - since so few systems >>>>>>>> use the rdfs semantics for subclass, very few systems when >>>>>>>> translating into RIF would use it in their translations. >>>>>>>> >>>>>>>> Same for below. You shouldn't translate ilog:subclass into >>>>>>>> rdfs:subclass. So, in fact, as far as we know, only rdfs based >>>>>>>> systems would ever use rdfs:subclass when translating through rif, >>>>>>>> and everyone else would have to invent their own. >>>>>>>> <chair> >>>>>>>> >>>>>>>>> Let's look at some other examples, like ILOG. From my limited >>>>>>>>> experience >>>>>>>>> with it, I remember that it uses Java as its data model. So, >>>>>>>>> suppose >>>>>>>>> there is a class foo in ILOG, which comes from Java. An ILOG >>>>>>>>> set of >>>>>>>>> rules must not derive "foo sub foo" because this is not true >>>>>>>>> in the data >>>>>>>>> model. However, it we translate Java subclass relationship into >>>>>>>>> rdfs:subclassOf then the resulting RIF translation should >>>>>>>>> generate "foo >>>>>>>>> sub foo". (In truth, as I recall, ILOG does not have "sub" in >>>>>>>>> the heads >>>>>>>>> of the rules, but it is easy to imagine that next year ILOG is >>>>>>>>> extended >>>>>>>>> with something like a query facility. Then their stock will >>>>>>>>> plummet >>>>>>>>> because their rule sets will not be faithfully exchangeable >>>>>>>>> through RIF >>>>>>>>> :-) >>>>>>> -- >>>>>>> Dr. Christopher A. Welty IBM Watson Research >>>>>>> Center >>>>>>> +1.914.784.7055 19 Skyline Dr. >>>>>>> cawelty@gmail.com Hawthorne, NY 10532 >>>>>>> http://www.research.ibm.com/people/w/welty >>>>>>> >>>>>>> >>>>>> >>>>> -- >>>>> Dr. Christopher A. Welty IBM Watson Research Center >>>>> +1.914.784.7055 19 Skyline Dr. >>>>> cawelty@gmail.com Hawthorne, NY 10532 >>>>> http://www.research.ibm.com/people/w/welty >>>>> >>>>> >>>> >>>> >> > -- Dr. Axel Polleres email: axel@polleres.net url: http://www.polleres.net/ rdf:Resource owl:differentFrom xsd:anyURI .
Received on Thursday, 13 December 2007 14:31:10 UTC