Re: [RIF] Reaction to the proposal by Boley, Kifer et al

From: Michael Kifer <kifer@cs.sunysb.edu>
Subject: Re: [RIF] Reaction to the proposal by Boley, Kifer et al 
Date: Wed, 03 May 2006 01:35:08 -0400

> 
> "Peter F. Patel-Schneider" <pfps@inf.unibz.it> wrote:
> > 
> > I, on the other hand, have some serious concerns with the proposal.  
> > 
> > I worry about using a substitution in the basis of the semantics of
> > conditions, in particular because the rest of the semantics of conditionals
> > (including the semantics of existentials) are unspecified in the proposal.
> > Will this actually end up close to a known logic?
> 
> This is based on a known logic: infinite Herbrand interpretations.

Reference, please.

> It is easy to extend this semantics for general, non-Herbrand domains.
> But this will be useful only for the FOL dialect. The others will have to
> fall back on Herbrand interpretations.

I worry about situations like the following.  

Suppose that there (only) are two constants, T and F, and (only) one
one-place function, N.  Does it then follow from the following two facts

	N(T) = F
	N(F) = T

that

	Ax Ey x = N(y)


[...]

> > I worry about the connection between the proposal and RDF and OWL.  I do
> > not view it as appropriate to relegate existing Semantic Web languages to
> > an add-on query interface.
> 
> Why?

Because we are supposed to be working within the confines of the Semantic Web.

> A query interface is a very general thing. 

Is it really?  It instead seems to me to be much more like a ghetto.  In
particular, the proposal uses a ternary predicate for RDF triples,
divorcing RDF facts like ex:a rdf:type ex:b from a representation
as ex:b(ex:a).

> It can range from seamless
> integration (e.g., in FOL-based dialects) 

How?  Can a query interface actually achieve complete integration?  For
example, can a query interface reasonably support a rule language that is
oblivious to the source of information, i.e., what sort of rule could be
used to produce the transitive closure of the binary relation R, where some
facts about R are in RDF and others are in the form of conditionless rules?

> to Rosati and Eiter et al. style integration, 

Perhaps.  These sorts of integrations do make a firm divide between "rule"
predicates and other predicates, so it may be more natural to "query" the
other predicates.  I am not totally convinced, even in this case.  I note
that the papers by Rosati et al. do not have a special query interface for
the other predicates.

> to external calls to ontologies. 

Well, I suppose that if the ontology cannot be changed then there is no
problem with a query interface.

> Different degrees of
> integration will be appropriate for different dialects. (For instance, what
> would be the appropriate integration for PR rules?)

Good question.  What answers are reasonable in this proposal? 

> 	--michael  

Peter F. Patel-Schneider

Received on Wednesday, 3 May 2006 11:27:36 UTC