W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2001

Re: namedNode? in predicate position?

From: <jos.deroo.jd@belgium.agfa.com>
Date: Sat, 8 Sep 2001 00:48:17 +0100
To: phayes@ai.uwf.edu
Cc: Graham.Klyne@Baltimore.com, w3c-rdfcore-wg@w3.org
Message-Id: <OFE284D479.7C351146-ON41256AC0.00802242@bayer-ag.com>

[...]
>> I have also found that to describe RDF-schema-based inferences, I
>> have wanted to construct expressions in which the RDF property is a
>> "variable".  I think the required effect could be achieved by means
>> other than "princeNode" arcs, but maybe less intuitive for a
>> developer.
>
> Yes, others have noted this also. OK,  this also can be allowed in
> the syntax without changing the MT; but I think that if we do allow
> this then I ought to rewrite the model theory slightly, because as it
> stands right now its not  quite clear what this would mean. The MT
> uses a standard logical device to describe existentials, basically
> saying that the existential is true

I would think *the assertion containing* the existential has a
truth value, not the existential itself

> if there is some interpretation
> of what it denotes that makes the assertion true. The trouble with
> this trick for relations (properties) is, that the simple denotation
> of a property isn't really all that important: what makes assertions
> involving it true or false are the *extensions* of those denotations.
> So a lot turns on whether those extensions are allowed to change when
> the denotation of the anonymous node is allowed to change.

I would think so, yes

> The only
> way to interpret this that would produce a reasonable proof theory
> would be to take the extension mappings as fixed and let just the
> denotations vary; which is what the MT says right now, in fact, but
> it ought to say it much more clearly and explicitly, since a lot
> hangs on that point if we are going to allow princeProperties.

that's nice
and again, thanks for the thing/extension distinction!

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Friday, 7 September 2001 18:49:02 EDT

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