W3C home > Mailing lists > Public > www-rdf-logic@w3.org > May 2001

Re: What do the ontologists want

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 15 May 2001 17:30:57 -0500
Message-Id: <v04210113b7275c57620c@[205.160.76.173]>
To: Uche Ogbuji <uche.ogbuji@fourthought.com>
Cc: www-rdf-logic@w3.org
> > Something that I very much wish to be able to do is something like this:
> >
> >    'Jon says "The sky is blue"'
> >    'I believe Jon'
> > =>
> >    'I believe (the sky is blue)'
> >
> > Or:
> >
> >    'Jon says "The sky is blue"'
> >    'My oracle says "Jon is reliable"'
> > =>
> >    'The sky is blue'
> >
> > I've deliberately not tried to state this rigorously, as I'd probably miss
> > the mark if I did.  I hope the general intent is reasonably clear.
> >
> > Maybe there is a way of formulating this that doesn't rely on logical
> > exotica.  But it does seem to rely on some form of "reflexion" -- a
> > statement is used both as an object about which other statements are made,
> > and as an assertion in its own right.
>
>I should note that I think you, Jonathan Borden and I are talking about one
>thing, and Pat Hayes is talking about an entirely different thing.  I think
>Pat is correct in his domain of discussion, but I personally am not working in
>that area in the forseeable future.

I would take it as a favor if you could take the time to briefly 
characterize the difference between what y'all are talking about and 
what I am talking about, in your view. My understanding of 
reification in RDF may, I concede, be lacking, but it is the best I 
can manage after about a year of careful reading and conversation 
with those working on RDF.

>I do think that RDF reification is an essential part of expressing what you,
>Jonathan and I have been talking about.

Reification is not needed to talk about attribution or belief, and 
indeed there are some well-known results due to Montague which show 
that modalities cannot be adequately modelled using reification.

>However, I am curious as to an accessible treatment of the logical rigor
>behind reification.  Clearly traditional FOL does not have the concept

KIF has a very elaborate machinery of meta-description, which I take 
to cover what you mean by reification. If you mean more than this, my 
imagination is insufficient.

>(although prolog introduces limited reification by such concepts as the
>definition of predicates).  Is it something that can be worked smoothly into
>the logical calculus?  I'd be surprised if not, given that I think it's such a
>natural fit in a system where propositions are modeled as a graph, as they are
>in RDF.

Modelling propositions in graphical form is on old game, arguably 
pre-dating modern logic. Peirce's original calculus (from the late 
1800s) is graphical, and many other graphical notations have been 
devised and are in widespread use. To the best of my knowledge, none 
of them use reification, however. I fail to see how reification 
arises naturally in graphical modelling; again, this seems to me to 
be based on a confusion between thinking of a graph arc as indicating 
reference, and thinking of it as indicating syntactic structure.

Pat Hayes

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Received on Tuesday, 15 May 2001 18:31:00 UTC

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