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Re: Reminder: pending discussion "membership" (pending discussion on ACTION-350)

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Fri, 07 Dec 2007 08:51:56 +0000
Message-ID: <475909AC.3010401@hplb.hpl.hp.com>
To: Michael Kifer <kifer@cs.sunysb.edu>
CC: axel@polleres.net, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Michael Kifer wrote:
> CSMA had an action to bug me about the ## feature :-)
> I thought that others might also be interested, so I am including my
> arguments below.
> 
> First, one needs to be able to specify that one class is a subclass of
> another class **as part of the KB**.

I disagree, at least if by KB you mean RIF rules rather than RIF rules + 
externally specified ontology or data model.

Expressing data models or ontological models and any subClass relations 
associated with them is not a RIF requirement.

> For instance, 
> 
> student##person.
> father(person)##person.
> 
> In KB apps this is used for reasoning, not just as part of a data
> model. How would one specify this info otherwise?

Using your data modelling language of choice. In the case of the 
Semantic Web stack, of which RIF is a part, the answer is RDFS/OWL.

In the case of XML Schema models then complex types can be related by 
both extension and restriction in ways that don't neatly map to subClass.

> Here is a more sophisticated example: parametrised lists.
> 
> list(?Subclass) ## list(?Super) :- ?Subclass ## ?Super.
> 
> (List of FOOs is a subclass of lists of BARs if FOO is a subclass of
> BAR. We could have list(father(person)), for example.)
> 
> RDF's subclassOf does not cut it because
> 
> 1. It imposes additional axioms, which are not commonly accepted.
> 2. It is also not even defined for classes specified using function terms
>    (like list(?Foo)).
> 
> Both arguments are also applicable to the RDF membership relationship.
> 
> I am convinced that throwing out these primitives serves no purpose and
> will just gratuitously cripple the BLD.

I am convinced that including these primitives moves RIF from the domain 
of rule interchange into that of data model interchange. Had that been 
explicitly part of the RIF charter I am not certain we would have 
approved the formation of RIF.

Dave
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Received on Friday, 7 December 2007 08:52:30 GMT

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