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Re: fulfilment of my action of today

From: Chris Welty <cawelty@gmail.com>
Date: Tue, 14 Aug 2007 21:25:43 -0400
Message-ID: <46C25617.3080707@gmail.com>
To: Michael Kifer <kifer@cs.sunysb.edu>
CC: RIF WG <public-rif-wg@w3.org>

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".

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.

>    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
Received on Wednesday, 15 August 2007 01:25:54 UTC

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