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RE: A triple is not unique.

From: McBride, Brian <bwm@hplb.hpl.hp.com>
Date: Mon, 20 Nov 2000 15:16:35 -0000
Message-ID: <5E13A1874524D411A876006008CD059F2394D7@0-mail-1.hpl.hp.com>
To: "'Jonas Liljegren'" <jonas@rit.se>, "McBride, Brian" <bwm@hplb.hpl.hp.com>
Cc: Dan Brickley <danbri@w3.org>, Seth Russell <seth@robustai.net>, RDF-IG <www-rdf-interest@w3.org>
[snip]

> Here is the example from M&S:
> 
>   <rdf:RDF
>     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>     xmlns:a="http://description.org/schema/">
>     <rdf:Description>
>       <rdf:subject resource="http://www.w3.org/Home/Lassila" />
>       <rdf:predicate 
> resource="http://description.org/schema/Creator" />
>       <rdf:object>Ora Lassila</rdf:object>
>       <rdf:type 
> resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement" />
>       <a:attributedTo>Ralph Swick</a:attributedTo>
>     </rdf:Description>
>   </rdf:RDF>
> 
> The example uses the property a:attributedTo.  You can't attribute an
> abstract statement to one person.  The example view the reified
> statement as a stating.

I disagree.  I may assert the statement S1.  You may assert it. Dan may
assert it.  This can be modelled just fine by adding a:attributedTo
properties as in the example you give above, quoting from M&S.


> 
> The reasoning for this is the same as before.  Let me repeat the
> example using This example.

No!  The claim was that the examples in M&S have a problem.  If that is
true, that could be good reason for changing M&S.  But the example you
use to point out a problem is not in M&S.  The examples in M&S work just
fine. 


[snip]

> > For the record, section 5, the formal model section of M&S states:
> > 
> >   There is a set called Statements, each element of which 
> is a triple
> >   of the form {pred, sub, obj}
> > 
> > That says that each Statement is a triple of the form (s,p,o).  A 
> > triple in mathematics is uniquely determined by its three 
> components.
> 
> Right.  But we can't say the same about the reified statement.  There
> can be many reifications of the same statement.

A good distinction.  Again from M&S 4.1:

  A new resource with the above four properties represents
  the original statement ...

The case to be met is that a statement is a triple (s,p,o) which
is uniquely defined by its three components.  The exert I just
quoted from M&S 4.1 says that a reified statement models a 
statement.  Not the stating of a statement.  Current M&S
implies therefore that a reified statement is uniquely determined
by its subject, predicate and object.

I appreciate the efforts you have just gone to be clear.  You have
helped my understanding of the issue.  If I remain unconvinced,
its not out of a lack of respect for your position.  However, it
seems to me that the answer is in M&S, though one has to search
for it.

Brian McBride
HPLabs
Received on Monday, 20 November 2000 10:16:56 GMT

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