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Re: reification "subagenda"

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Thu, 14 Feb 2002 17:21:19 +0000
Message-Id: <5.1.0.14.2.20020214170837.038e45a0@joy.songbird.com>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org
At 04:18 PM 2/13/02 -0600, Dan Connolly wrote:
>I really wrestle with this. The M&S spec is quite clear that
>the answer is YES, as PeterPS has pointed out in
>his message to www-rdf-logic of 04 Feb 2002 13:24:08 -0500.

I read PeterPS' message on RDF-logic, and was not convinced by it that RDF 
M&S is clear about this issue:

[[[
If you read the RDF M&S there are quite clear statements of the status of
reified statements.

         A statement and its corresponding reified statement exist
         independently in an RDF graph and either may be present without the
         other. [RDF M&S, 4.1]

This sentence does not admit multiple reified statements for a single
statement.

RDF M&S is also quite clear that only one statement can exist with the same
subject, predicate, and object.

         There is a set called Statements, each element of which is a triple
         of the form {pred, sub, obj} [RDF M&S, 5]

Just afterward there is more wording that indicates that a statement can
only have one reification

         ... we can express the reification of this as a new resource
         ... [RDF M&S, 5]

So, for any triple there is at most one statement, and for every statement
there is at most one reification.
]]]

1. I agree that M&S allows only one statement with given sub, pred, obj.

2. M&S may not specifically admit more than one reification of a statement, 
but it also does not (to me) clearly deny the possibility.

3. The sentence containing "express the reification" would suggest only one 
reification, but that's a lot of consequence to hang on one use of a 
definite article (as opposed to an indefinite article).

So, while the spec *can* be read as indicating only one reification per 
statement, I would disagree that it is clear about this.  I wouldn't design 
software around that assumption on the basis of what I read in M&S.

#g
--

>On Wed, 2002-02-13 at 16:18, Frank Manola wrote:
>[...]
> > 1.  Brian suggests that we (explicitly) decide on answering the
> > question:  Does
> >
> >    <stmt1> <rdf:type> <rdf:Statement> .
> >    <stmt1> <rdf:subject> <subject> .
> >    <stmt1> <rdf:predicate> <predicate> .
> >    <stmt1> <rdf:object> <object> .
> >
> >    <stmt2> <rdf:type> <rdf:Statement> .
> >    <stmt2> <rdf:subject> <subject> .
> >    <stmt2> <rdf:predicate> <predicate> .
> >    <stmt2> <rdf:object> <object> .
> >
> >    <stmt1> <property> <foo> .
> >
> >    entail:
> >
> >    <stmt2> <property> <foo> .
> >
> > [Brian suggests that the answer is NO]
>
>I really wrestle with this. The M&S spec is quite clear that
>the answer is YES, as PeterPS has pointed out in
>his message to www-rdf-logic of 04 Feb 2002 13:24:08 -0500.

------------------------------------------------------------
Graham Klyne                    MIMEsweeper Group
Strategic Research              <http://www.mimesweeper.com>
<Graham.Klyne@MIMEsweeper.com>
Received on Thursday, 14 February 2002 12:56:28 EST

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