Re: Friendly amendment to rif:subClassOf

> Michael Kifer wrote:
> > Actually, semantically rdfs:subClassOf is a subrelation of rif:subClassOf.
> > Not the other way around.
> 
> </chair>
> I went back and forth on this.  I'm not sure it matters that much, as 
> long as rif:subclass is not reflexive.   Since you haven't formally 
> defined the semantics of rif:subclass yet, we could go either way.

The semantics has been defined formally. But you are right.
foo rif:subclassOf bar should imply foo rdfs:subclassOf bar.
I wrote my reply before having my morning coffee.

But I do not really see how your proposal is a compromise. It is just a
statement of a fact.  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.


	--michael  

> 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
> 
>

Received on Thursday, 16 August 2007 13:07:58 UTC