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Re: AtomList infinite or cyclic in all models

From: Ian MacLarty <iml@missioncriticalit.com>
Date: Thu, 22 Feb 2007 11:30:27 +1100
To: "Lynn, James (Software Escalations)" <james.lynn@hp.com>
Cc: Pat Hayes <phayes@ihmc.us>, "Henry S. Thompson" <ht@inf.ed.ac.uk>, www-rdf-rules@w3.org
Message-ID: <20070222003027.GA2876@cleopatra>

On Wed, Feb 21, 2007 at 05:15:40PM -0500, Lynn, James (Software Escalations) wrote:
> 
>  
> 
> -----Original Message-----
> From: www-rdf-rules-request@w3.org [mailto:www-rdf-rules-request@w3.org]
> On Behalf Of Pat Hayes
> Sent: Wednesday, February 21, 2007 17:02 PM
> To: Henry S. Thompson
> Cc: www-rdf-rules@w3.org
> Subject: Re: AtomList infinite or cyclic in all models
> 
> >> So a collection ends when you find rdf:nil as the value of rdf:rest
> (no matter what else might be in the description); rdf:nil is an atom,
> if you like, but it's not an *element* of the collection unless its the
> value of rdf:first on some subcollection before the first rdf:nil value
> of an rdf:rest. <<
> 
> So this clears up the whole problem of disjoint lists both having an
> element in common (i.e. rdf:nil), right?
> 

No it doesn't.  The problem is independent of how you interpret lists.
According to the owl semantics, if the triple <rdf:nil rdf:first rdf:nil>
exists, then rdf:nil is a member of the class Atom, because of the
allValuesFrom(Atom) constraint on rdf:first.  If we have another
class, say X, and we introduce the constraint that Atom is disjoint with
X, then we cannot define a list of X's in the same way we define a list
of Atoms without making the ontology inconsistent, because then rdf:nil
is a member of both X and Atom (regardless of how you interpret lists).

Ian.
Received on Thursday, 22 February 2007 00:31:29 UTC

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