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Re: Proposal to resolve ISSUE-81

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 28 Mar 2008 08:41:36 -0400 (EDT)
Message-Id: <20080328.084136.67420521.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: schneid@fzi.de, alanruttenberg@gmail.com, public-owl-wg@w3.org

[I've restored some context in this email thread so that I can try to
defend Michael's point.]

From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: Re: Proposal to resolve ISSUE-81
Date: Fri, 28 Mar 2008 09:28:58 +0000

> Michael Schneider wrote:
> 
> > But now another more practical point comes to my mind.
> > 
> > Negative property assertions in OWL-1.1, although only being
> > syntactic sugar, allow ontology authors to express in an explicit
> > form that a certain assertion is *not* expected to hold. Further, it
> > might well be that explicit negative assertions will have
> > computational advantages, when it comes to check for consistency. 
> > 
> > I also want these advantages in RDF, not only in functional syntax. 
> > And for the aspect of semantical and computational complexity: The
> > way you suggest to encode negative assertions requires a pretty
> > bit of OWL language features (equivalence, intersection, nominals,
> > restrictions, and owl:Nothing). I believe a small rulebased sublanguage 
> > of OWL-Full will easily be out of play here.
 
> Negative assertions seem to me to be well out of scope of the design
> of RDF, and unlikely to be implementable in an interioperable way in
> typical RDF systems. 
> 
> I think your 'want' here is unreasonable - if you really want this
> expressivity then take the OWL baggage. 
> 
> Jeremy

Michael's wants appear to me to be quite reasonable.

To me what he wants is that the use of negative assertions only requires
a certain kind of simple expressive power on the RDF side. This would
allow stating something like the following

	a r b
	NOT ( a r b )

in a way that is not too foreign to RDF, i.e., certainly not depending
on semantic support for restrictions with nominals.

Whether this is in the "scope of the design of RDF" is debatable.  Even
RDF itself has contractions so one cannot argue from any claimed
contradiction-free status for RDF.

peter
Received on Friday, 28 March 2008 12:50:30 GMT

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