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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 19:43:12 +0100
Message-ID: <3BD70BC0.8040507@hplb.hpl.hp.com>
To: fmanola@mitre.org
CC: Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org
Hey Frank,

Frank Manola wrote:

> Brian--
> It's not clear to me what distinguishing "statement" and "triple"
> accomplishes in this context.  

I found I could make best sense of M&S with the distrinction, and hoped to 
reduce confusion.  I should have known better, I suppose.

I tried to emphasize that this was my *personal* reading of M&S.  I don't intend 
to try to defend it as the 'one true way' (I've learnt something over the past 
few months.)

>Are we doing "uses" and "mentions"
> again?  The M&S (Section 5) says:
> "(P162) There is a set called Statements, each element of which is a
> triple of the form 
>  (P163) {pred, sub, obj}"
> I naturally read that as saying that the triples were statements as far
> as RDF was concerned (if they weren't, why wasn't the set called
> "Triples" instead of "Statements"?).  Morever:
> "(P179) From the standpoint of an RDF processor, facts (that is,
> statements) are triples that are members of Statements."
> I'd agree that the M&S is not a canonical example of precise language,
> but as long as we're talking about what the M&S says (or seems to say!),
> it seems to say to me that triples are statements.

Fair enough.  I'll try to remember that is your model in discussion.

> Regarding the graph representation:
> "(P165) We can view a set of statements (members of Statements) as a
> directed labeled graph: each resource and literal is a vertex; a triple
> {p, s, o} is an arc from s to o, labeled by p. " 
> This says a triple is an arc in the graph.  So if a triple is a
> statement (by my reading), then an arc is a statement.  Maybe some more
> elaboration would help.  When you say:
>>If I write:
>>>   <:sky> <:is> <:blue> .
>>>   <:sky> <:is> <:blue> .
>>>I clearly have two triples. 
> Do you?  Or do you have two lines of structured text that represent the
> same triple?

> The same problem exists with "tuples".  You said:
>>>   o a statement is an abstraction; its a tuple with three components, subject,
> If distinct tuples are identified by three distinct components, then
> however many times I write the same three components down, I've still
> stated only one tuple. 

> Is a triple identified only by its components,
> or by something else too?  If I say "Frank is confused" 500 times, have
> I made 500 (true) statements, or only one?

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.

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.  What does reification mean in those terms?

And for failing to keep to my own rule, I appologise and will slap myself silly 
all the way home.

Received on Wednesday, 24 October 2001 14:48:36 UTC

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