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Re: reification test case

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 04 Feb 2002 13:49:59 -0500
To: seth@robustai.net
Cc: www-rdf-logic@w3.org
Message-Id: <20020204134959J.pfps@research.bell-labs.com>
From: "Seth Russell" <seth@robustai.net>
Subject: Re: reification test case
Date: Mon, 4 Feb 2002 10:41:21 -0800

> From: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
> 
> > 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.
> 
> Well then that should be amended to read:
> 
>      A statement and its corresponding reified statement[s] exist
>      independently in an RDF graph and either may be present
>      without the other.

There are arguments to be made on either side.  Some argue that there
should be multiple reifications, some argue that there should not. Given
that there are two viable possibilities, and that RDF M&S clearly comes
down on one side, switching to the other is a significant change, and
should not be made lightly.

> > 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]
> 
> There is only the one proposition .. so what?
> 
> > Just afterward there is more wording that indicates that a statement can
> > only have one reification
> >
> > ... we can express the reification[s] of this as a new resource[s]
> > ... [RDF M&S, 5]
> >
> > So, for any triple there is at most one statement, and for every statement
> > there is at most one reification.
> 
> I fixed that too.
> 
> But the essential requirement that you will need to answer is not a
> legalistic one, but a practical one.  If you throw out the ability to have
> multiple descriptions of statements, then how are we to describe multiple
> occurances of the same proposition relative to the contexts in which they
> appear?

Well I guess then you can't, at least not with RDF reification.

> Seth Russell

RDF reification is what is described in RDF M&S.  It may not be very
useful but that doesn't mean that RDF reification should be something
different from what is described in RDF M&S.  (There are enough unclear
aspects of RDF M&S to argue over without changing the clear parts.)

Peter F. Patel-Schneider
Bell Labs Research
Received on Monday, 4 February 2002 13:51:50 GMT

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