W3C home > Mailing lists > Public > www-rdf-logic@w3.org > January 2005

RE: RDF as a syntax for OWL

From: Geoff Chappell <geoff@sover.net>
Date: Thu, 6 Jan 2005 22:26:27 -0500
To: "'Peter F. Patel-Schneider'" <pfps@research.bell-labs.com>
Cc: <bparsia@isr.umd.edu>, <www-rdf-logic@w3.org>
Message-ID: <007101c4f468$b7e0ddc0$6401a8c0@gsclaptop>



> -----Original Message-----
> From: www-rdf-logic-request@w3.org [mailto:www-rdf-logic-request@w3.org]
> On Behalf Of Peter F. Patel-Schneider
> Sent: Thursday, January 06, 2005 5:42 PM
> To: geoff@sover.net
> Cc: bparsia@isr.umd.edu; www-rdf-logic@w3.org
> Subject: Re: RDF as a syntax for OWL
> 
> 
> From: "Geoff Chappell" <geoff@sover.net>
> Subject: RE: RDF as a syntax for OWL
> Date: Thu, 6 Jan 2005 11:50:42 -0500
> 
> > > 3/ How will your code handle
> > >
> > > 	_:x rdf:type owl:Restriction .
> > > 	ex:p1 rdf:type owl:ObjectProperty .
> > > 	ex:c1 rdf:type owl:Class .
> > > 	_:x owl:onProperty ex:p1 .
> > > 	-:x owl:someValuesFrom ex:c1 .
> > > 	_:x owl:allValuesFrom ex:c1 .
> >
[...]
> 
> > I suppose the right thing to do would be to flag the restriction as
> > malformed? If so, I imagine rules along the lines of these could be
> used:
> 
> Is it malformed?  This is part of the problem with using RDF as a syntax
> carrier.

I guess I assumed that the point of the nnf exercise was extracting class
descriptions in suitable form from a owl/rdf file to feed to a DL engine of
some sort and so the usual DL-ish restrictions applied (e.g.:
http://www.w3.org/TR/owl-ref/#Restrictions). In that case, yes, I would say
it's malformed. I guess it's blurrier if it's owl full we're talking about.
BTW, are you aware of any formal statements about the semantic impact of
malformed restrictions anywhere in the owl specs? I've seen some in drafts,
but couldn't find anything in the current docs.

I do recognize the difficulties involved here - there's no denying it's ugly
to have to decree that certain triple patterns are disallowed or are
required in your graph or you risk pockets of poorly defined meaning.


[...]

> > The smearing of higher-arity relations into triples is seemingly the
> source
> > of much pain when trying to use RDF as a syntax for other languages (due
> to
> > the fact that you can't really constrain the triples so that only valid
> and
> > complete instances of the relation can be represented).
> 
> Well, this is indeed part of the problem, but there are lots more, having
> to do with the open-world flavour of RDF, the non-tree flavour of RDF, and
> the triples-only flavour of RDF.
> > I'm not sure that
> > represents the same problem when using RDF to represent incomplete
> knowledge
> > (from one or more sources) - in fact it probably becomes a strength.
> 
> Maybe, but part of the point is that syntax doesn't fit into any of RDF
> strengths.
>

:-)
 
> peter

Geoff
Received on Friday, 7 January 2005 03:26:57 UTC

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