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Re: Technical tweaks to the MT, for reviewers.

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 08 Nov 2002 16:36:20 -0500 (EST)
Message-Id: <20021108.163620.86422628.pfps@research.bell-labs.com>
To: phayes@ai.uwf.edu
Cc: w3c-rdfcore-wg@w3.org, herman.ter.horst@philips.com

From: pat hayes <phayes@ai.uwf.edu>
Subject: Re: Technical tweaks to the MT, for reviewers.
Date: Fri, 8 Nov 2002 15:20:38 -0600

> >From: pat hayes <phayes@ai.uwf.edu>
> >Subject: Technical tweaks to the MT, for reviewers.
> >Date: Fri, 8 Nov 2002 11:47:33 -0600
> >
> >>
> >>  1. There is a problem I mentioned earlier with literals like
> >>  "badnumber"^^xsd:integer . They have to denote something, but they
> >>  shouldn't denote a literal value (because they, er, don't, right?)
> >>  The trouble is that until we go ask the datatype, RDF can't tell the
> >>  difference between one of these and "12345"^^xsd:integer. So in the
> >>  basic RDF MT, we need to say that typed literals denote something but
> >>  we don't yet know even if its a literal value, so it has to be in IR,
> >>  not in LV (as at present).
> >>
> >>  So what do we do when we find out that it is bad? The current draft
> >>  invents an ad-hoc thingie (a triplet) to be the value in this case,
> >>  but that is not a good solution. Better would be to say that it
> >>  denotes some unknown but arbitrary thing which, whatever it is, is
> >>  not a literal value. This adds a slightly odd technical extension to
> >>  the definition of datatyped interpretation, which will now include a
> >>  new mapping IBL from datatyped literals to things in IR that are
> >>  *not* in LV, which are the 'things' that the literal will denote *if*
> >>  it is badly typed.
> >
> >I think that I would prefer the interpretation of bad literals to be
> >elements of LV that are not in L2V for any datatype.  I think that this is
> >just a stylistic preference, but there may be consequences in
> >more-expressive languages (such as OWL, but I can't think of any).  Perhaps
> >the easiest way to go would be to require bad literals just not to denote
> >anything in any datatype value space, and leave whether they are in LV
> >open.
> 
> OK, I see what you mean, but not how to do it elegantly. 

Agreed.   I'm not unhappy with the way you suggest, so why not go your way,
and I'll see how to work with it in OWL.  If it causes problems, we'll just
have to figure out a solution.  :-)

> There is no 
> way to refer to the set of things in any L2V value space..... Of 
> course I could introduce one, but then what is the point of having LV 
> ?
> 
> The difference in entailments is whether we want
> 
> aaa ppp <any literal, even a bad one>
> 
> -->
> 
> aaa ppp _:xxx .
> _:xxx rdf:type rdfs:Literal .
> 
> Right now, it does not; this works only for good literals. If we say 
> it does, then is there any way to distinguish good from bad literals?
> 
> Pat

peter
Received on Friday, 8 November 2002 16:36:31 EST

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