W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > January 2002

RE: TDL Model Theory

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Fri, 25 Jan 2002 11:00:37 +0000
Message-Id: <5.1.0.14.2.20020125105247.00a98510@joy.songbird.com>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: <w3c-rdfcore-wg@w3.org>
At 02:50 PM 1/24/02 +0000, Jeremy Carroll wrote:
> >
> > I have a couple of comments/questions...
>
>I'll try and answer.

Thanks... mostly this confirms what I expected.

[...]
> > So the denotation of a node labeled with "10" and type-designated to be a
> > decimal integer can never be exactly the same as a node the
> > denotes just an
> > integer value that is, say, the count of my fingers-and-thumbs, without
> > regard for how it is lexically represented.   (I don't see this as a
> > problem, but note that it seems like a departure from previous
> > approaches.)
>
>Yes, but such nodes don't exist in the models ... unlike S-A, (or the
>original P), at least in the model theory all values (such as integers) are
>always paired with a lexical representation.

So, in effect, the denotation of *any* node is a pair (in any model of an 
RDF graph)?

[...]
>I want rdf:value as the identity which is why its Universe x Universe.

OK.

> > Something thing that is bothering me about this is:  the
> > interpretation of
> > a Unicode node is stated in such a way that there may be several
> > literal-value pairs that could be denoted.  Do you mean the
> > interpretation
> > in this case to be ambiguous?
>
>Extremely. I am trying to delete the suggestion that xsd:string is the
>default type.
>
>If we support no types, or no type information is available for a particular
>node labelled "foo", then that node can be interpreted as a pair <"foo", x >
>for any x what so ever.
>
>It's model theory not application semantics.

Ah, I think I get it.  In any model (which in your MT is defined relative 
to some set of datatypes as well as the URI vocabulary), the interpretation 
can be _any_ pair of <literal,value> that is a member of some datatype 
mapping.  rdf:type and schema statements may have the effect of eliminating 
some potential candidates from the set of models?

[...]
> > There is no defined lexical form that universally denotes me, the
> > person.  So what is the denotation of the thing labelled _:gk ?
>
>Pass for now.

I think this would need to be addressed, but I now don't see it as a big 
deal.  I suppose one could add a "bottom" or "null" to the literal domain 
and use that?

#g


------------------------------------------------------------
Graham Klyne                    MIMEsweeper Group
Strategic Research              <http://www.mimesweeper.com>
<Graham.Klyne@MIMEsweeper.com>
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Received on Friday, 25 January 2002 08:28:14 EST

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