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Re: Properties not predicates (was Re: PRIMER: draft data modelsection)

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Thu, 25 Oct 2001 19:36:44 +0100
Message-ID: <3BD85BBC.7C1755A1@hplb.hpl.hp.com>
To: w3c-rdfcore-wg@w3.org


Pat Hayes wrote:
> 
> Look, model theory is just being clear about meanings. If you have
> something central in the language that is outside the semantic
> theory, you are just admitting to confusion. If you (or anyone) can
> come up with a coherent story about what this kind of reification is
> supposed to mean, I can build that meaning into the MT.  But right
> now, there doesn't seem to be a coherent story.

I really don't think reification is the sort of thing that model theory
is meant to help clarify.


I guess for me reification is, to use Bill's words, a way of making
Statements about Statements.

To clarify this I guess *I* would introduce the (maligned) concept of
'stating'.

What's being reified is the occurrence of a statement in a document.
This is how I make sense of the provenance examples in M&S. Provenance
rather than logic are the motivators for reification. 

Hence, when we see a triple in a document we reify in order to make
statements about who wrote it, when it was said, etc. We may also
indicate who believes it, but this 'belief' would not be in a logician's
sense but in a more human sense.

When two different documents contain the same triple, then the two
statings (triple occurrences) are distinct and different provenance is
attached to them. Also, for those of us who assign our belief on the
basis of past experience and reputation rather than through having
personal opinion about all facts, belief is related to provenance. So my
belief or disbelief in one and the same triple may be different in
different statings because of the author.

Thus I do not see reification as a process for making meta-statements at
the logic level, and hence I see it as not an appropriate topic for the
model theory.

Concerning meta-statements at the logic level here is an example, that I
would feel somewhat unhappy with:

<rdf:RDF xmlns:rdf="..." xmlns:rdfe="...">
  <rdf:Description rdf:ID="subj">
   <rdf:value rdf:ID="explicit" rdf:resource="#obj" />
   <rdf:value rdf:ID="existential" ><rdf:Description /> </rdf:value>
  </rdf:Description>
  <rdf:Description rdf:about="#explicit">
    <rdfe:entail rdf:resource="#existential" />
  </rdf:Description>
</rdf:RDF>

where the last triple says that the triple

<#subj> <rdf:value> <#obj> .

entails

<#subj> <rdf:value> _:bnode .

That to me is not what reification is about.


Jeremy
Received on Thursday, 25 October 2001 14:32:16 EDT

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