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Re: Properties not predicates (was Re: PRIMER: draft data model section)

From: Frank Manola <fmanola@mitre.org>
Date: Wed, 24 Oct 2001 15:37:00 -0400
Message-ID: <3BD7185C.FABDC8E4@mitre.org>
To: Brian McBride <bwm@hplb.hpl.hp.com>
CC: Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org
Brian McBride wrote:
> 
snip
> 
> This sort of discussion can rathole deep and long.  I've seen it many times
> before on rdf interest and elsewhere and never get anywhere.

I agree.  

> 
> It was for this, if for nothing else, that I wanted us to have a model theory.
> Please, please, lets try to stick with the concepts we have a formal
> mathematical definition for in the model theory.  We have nodes and arcs and
> labels. 

OK, but a slight quibble at this point:  I want the model theory to help
define and clarify the concepts we need to be using, but if we find we
need other concepts, I want to change the model theory to cover them,
not throw out the concepts because they aren't in the model theory.  

Now to your point:  I think the model theory has the concepts we need
(possibly not using the same terms though).  In the model theory, we
also have "asserted triples".  Also, in Section 2.1, there is also the
statement: "An arc labeled with p from a node n1 to a node n2 maps [in
logic] to an atomic assertion that the relation p holds true between the
expressions s and o gotten by translating n1 and n2 respectively [to the
appropriate logical constants] (written as (p s o) in KIF syntax)..."  I
would say that the thing that is an "assertion" in logic is a
"statement" in RDF [assuming we're dealing with only "asserted triples"
at the moment.  What is that (p s o) thing in KIF syntax called?]  This
was (as I understood it) the basis of all our discussions about the
equivalence of RDF to a simple form of EC logic (using only binary
properties.  (In fact, if I remember correctly, at one time those things
we now call "statements" used to be called "assertions" in RDF).  The
point is, we need more than nodes, arcs, and labels, we need things
whose denotations are true or false.  The model theory says those things
are asserted triples s p o (which I interpret as being the RDF syntax
for a statement, like "Ora Lassila created <foo>").  Is the problem
whether we're talking about the syntax (the RDF side) versus the
interpretation?

> What does reification mean in those terms?

Talk about a rathole!  How did reification get into this?  

--Frank


-- 
Frank Manola                   The MITRE Corporation
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Received on Wednesday, 24 October 2001 15:41:30 EDT

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