Re: AtomList infinite or cyclic in all models

On Thu, Feb 15, 2007 at 10:55:36AM +0000, Dave Reynolds wrote:
> 
> Bijan Parsia wrote:
> >On Feb 15, 2007, at 9:57 AM, Dave Reynolds wrote:
> >
> >>Ian MacLarty wrote:
> >>>Hello,
> >>>In the owl file http://www.daml.org/rules/proposal/swrl.owl, the
> >>>AtomList class is a subclass of rdf:List and places cardinality
> >>>restrictions of 1 on rdf:first and rdf:rest.  Furthermore rdf:rest for
> >>>AtomList is constrained to the range AtomList.
> >>>This seems to imply that in all models, AtomList will be either infinite
> >>>or cyclic.
> >>>Could someone comment on this definition of AtomList?
> >>
> >>This is a list for the RIF rules working group
> >
> >No, it isn't:
> >    <http://lists.w3.org/Archives/Public/www-rdf-rules/>
> >
> >"""This mailing list is intented for the discussion of queries and rules 
> >for RDF data. We invite practical discussions with the goal of 
> >coordination and shared understanding of other implementations. See the 
> >list of lists for related mailing lists and a description of their 
> >intended content."""
> >
> >and:
> >    <http://lists.w3.org/Archives/Public/www-rdf-rules/2001Jul/0000.html>
> >
> >"""This is a subgroup of RDF Interest to discuss rules and query for RDF 
> >and
> >DAML+OIL.  It may later recommend that a working group be started for
> >Rules/Query.""""
> >
> >>and not a support list for SWRL.
> >
> >It is, of course, not a support list of any kind, but a discussion list. 
> >However, most W3C discussion lists that I've been on welcome *this* sort 
> >of question.
> 
> My apologies. I seem to have a misconfigured set of mail filters which 
> put this message in the same bucket as RIF, I should have read the mail 
> headers more carefully. This is indeed an entirely appropriate place to 
> ask such a question.
> 

No problem.  By the way I got this mailing list address directly from
http://www.w3.org/Submission/SWRL/, where it states
"Public comment on this document is invited on the mailing list
www-rdf-rules@w3.org".

Now, back to the issue at hand.  For me, having rdf:nil a member of
AtomList as it stands is problematic, since it means that in all models
rdf:nil must have values for the rdf:first and rdf:rest properties,
because of the cardinality restrictions imposed by AtomList.

If AtomList were renamed to "NonEmptyAtomList" and AtomList was instead
defined as the union of NonEmptyAtomList and the singleton set
containing rdf:nil, then I believe the problem would go away.

Ian.

Received on Friday, 16 February 2007 00:02:50 UTC