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Re: Statements/Reified statements

From: Graham Klyne <GK@Dial.pipex.com>
Date: Wed, 22 Nov 2000 22:50:42 +0000
Message-Id: <>
To: Sergey Melnik <melnik@db.stanford.edu>
Cc: ML RDF-interest <www-rdf-interest@w3c.org>
At 01:52 PM 11/22/00 -0800, Sergey Melnik wrote:
>Pierre-Antoine CHAMPIN wrote:
> > ...
> > First, Statements and Reified statements are not the same thing.
>Although this is consistent with the spec, I believe there are
>significant advantages both for understanding and manipulating reified
>statements if these two notions are merged into one.
>Can you (or anyone) list some use cases where it is beneficial to make
>this distinction? I can think of several cases, in which distinguishing
>statements vs. reified statements makes things a lot more complicated.
>Just consider a database query that retrieves all assertions made about
>a statement (by anyone).

I think it is necessary to distinguish between 'statings' and 'quotings' of 
statements.  Reification is a way to do that within the RDF model as 
currently defined.  Are there others?

>The "fix" or interpretation I advocate is the following:
>- STATEMENTS ARE RESOURCES (that implies that every statement is unique
>and equivalent to reified statement)
>- toss "quad" reification mechanism altogether

As I follow this debate, I become more convinced that the idea of a 
reification as a "model" of a statement is most helpful.  It allows us to 
create such a model, with associated resource ID, so we can make statements 
like "A statement of the form [p s o] was asserted and signed by Alice", 
and also "A statement of the form [p s o] was asserted and signed by 
Bob".  Here, we actually _need_ two separate resources to express this 
without also saying "A statement of the form [p s o] was asserted by Alice 
and signed by Bob".

Thus, I suggest, we actually need to be able to have multiple resources 
representing a given statement.  The RDF model achieves this through 
reification.  The XML syntax and any implementation may provide a shorthand 
for the reification quad.


Graham Klyne
Received on Wednesday, 22 November 2000 18:09:40 UTC

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