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

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Wed, 24 Oct 2001 17:47:08 +0100
Message-ID: <3BD6F08C.7050703@hplb.hpl.hp.com>
To: Pat Hayes <phayes@ai.uwf.edu>
CC: w3c-rdfcore-wg@w3.org


Pat Hayes wrote:

>> Just checking we are clear what is being renamed.
> 
> 
> Well, I thought I was clear, but now I am completely confused.
> 
>>  M&S uses the term predicate for a component of a statement.
> 
> 
> That means a triple, right? Or a [node/edge/node] combination in an RDF 
> graph. Or does 'statement' mean something else? Right now, as I 
> understand it, there are triples in Ntriples,  pieces of graph in the 
> graph syntax, and more complicated pieces of syntax in RDF/XML. Which of 
> these is called a statement?


You have put your finger on a key question, that I think we need to get clear if 
  we are to reconcile the language of the old M&S with the new model theory.

We are dealing here with two formal models.  M&S has a formal model, and we have 
the new model theory.  I think that M&S has the concept of statement and the new 
model theory does not.

My *personal* reading of M&S is that statement and triple meant two different 
things.

   o a statement is an abstraction; its a tuple with three components, subject, 
...

   o a triple is a concrete representation of a statement, e.g. state in a 
computer memory, markings on paper etc.

[I'm not defending this model; I'm just trying to express it.  It may well be 
full of contradictions]

How do these concepts relate to the new model theory.  Well, a triple in 
n-triples is pretty clearly still a triple.  What is an arc in a graph?  Not a 
statement, I think.  If I write:

   <:sky> <:is> <:blue> .
   <:sky> <:is> <:blue> .

I clearly have two triples.  I would also have two arcs in one of your graphs 
(until it got tidied).  But to M&S, (as I interpret it, others would disagree) 
there is only one statement, because both triples denote the same statement.

I find no concept similar to statement in the new model theory.

Brian
Received on Wednesday, 24 October 2001 12:51:43 EDT

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