Re: fulfilment of my action of today <-- Rumblings on why we need classification terms in RIF (and why RDF's vocab should not be used)

> Out of interest (and apologies for the naïve qu's): 
> 1. what would be an example rule here? 
> eg: C1 is a subclass of C0 
> [and by implication C1 inherits properties, maybe default values for such properties, from C0, and inherits method definitions, all subject to any intermedia
> te subclass definition overrides]?

does not need to be a rule. could be just a fact like
phdstudent##student.
(If one could write something like that in PR).

> 2. note that for a PR, as discussed in the call yesterday, the most likely equivalents would be:
> - do a class membership query on some instance in a rule condition [not really a subclass test as class relationships are metamodel constructs]
> - allocate an instance to some new class [not supported in most PR engines due to their Java object model base]
> 
> The above might explain why for the PR community the question on whether RIF supports this construct is somewhat irrelevant. I can't think how a PR translato
> r would handle such a construct without recreating/simulating an OO model semantics dynamically or getting into code generation...  

I said that the most likely scenario would be querying. Although current
PR languages tend not to support queries, they might in the future.


	--michael  


> [My 2cents contribution is that RDF vocab should only be used if RDF is the only "rule language / data model" requiring this feature OR RDF vocab is a suffic
> ient abstraction of all "rule language / data model"s requiring this feature].  
> 
> Paul Vincent
> TIBCO | ETG/Business Rules 
>  
> > -----Original Message-----
> > From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
> > On Behalf Of Chris Welty
> > Sent: 15 August 2007 02:26
> > To: Michael Kifer
> > Cc: RIF WG
> > Subject: Re: fulfilment of my action of today
> > 
> > 
> > 
> > 
> > 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
> 
> 
>

Received on Thursday, 16 August 2007 07:54:57 UTC