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

Re: Reification as nesting

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 19 Jun 2001 12:28:52 -0500
Message-Id: <v04210106b75538f23dc3@[205.160.76.208]>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: Drew McDermott <drew.mcdermott@yale.edu>, www-rdf-logic@w3.org
>pat hayes wrote:
> > Seems to me that
> > introducing contexts or quads or whatever are all much bigger changes
> > to the RDF model than introducing what amounts to a new category of
> > triple (or just changing the spec so that some of the old triples
> > have a different interpretation.)
>
>
>M&S discusses the concept of a 'model' or 'graph' aka context
>aka StatementSet - essentially being a set of statements.  Unfortunately
>it doesn't make any mention of this concept in the section 5.
>
>Thus this concept does not have to be introduced to RDF, but it does
>need to be better defined.

I took it that the 'graph' described in M&S was not an entity, but a 
way of thinking about RDF as a whole. A kind of graphical abstract 
syntax for the entire language, rather than a syntactic construct.

>For my money a lump of RDF/XML or N3 represents a set of Statements and
>we can talk about whether a statement is a member of that set or not,
>something I find clearer than talking about whether a statement is
>'asserted' or not.

The issue however is whether these sets can themselves be 
incorporated into sentences. Adding that ability changes the language 
profoundly.

BTW, a problem with the above (for me) is that when used in the ways 
I want to use them, many of the triples inside such a set are not 
statements - they don't have truthvalues or express a proposition. 
Maybe this is just a terminological quibble, but it does have a 
nonterminological consequence when trying to define a coherent 
semantics, because we need a way to distinguish the 'real' statements 
from the mere parts of other, larger, statements.

>N3 introduces a syntax for embedding the respresention of such a set
>of statements (N3 calls them contexts) inside the representation of another,
>a feature RDF/XML current lacks.

Well, sorry again to quibble, but N3 didnt *introduce* such a syntax. 
If anyone did, it was probably one of Peirce, Frege or Aristotle, 
although one could make a pretty good case that it was the first 
proto-human who ever thought of writing down speech, probably in 
ancient Sumeria.

BTW, I have yet to discover what exactly a 'context' is in N3. Is N3 
supposed to be syntactic sugar for a particular way of writing RDF, 
or is it a different language altogether?

Pat Hayes

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Received on Tuesday, 19 June 2001 13:28:55 GMT

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