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Re: single-ID constraint not clear [Fwd: Re: Guide: Legal syntax?]

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 30 Oct 2002 07:13:40 -0500 (EST)
Message-Id: <20021030.071340.09104343.pfps@research.bell-labs.com>
To: dave.beckett@bristol.ac.uk
Cc: connolly@w3.org, www-rdf-comments@w3.org, michael.smith@eds.com

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Subject: Re: single-ID constraint not clear [Fwd: Re: Guide: Legal syntax?] 
Date: Wed, 30 Oct 2002 10:21:36 +0000

> >>>Dan Connolly said:
> > I don't have any replacement text to suggest just now,
> > but I have to agree with Peter's observation
> > that the existing text isn't clear.
> 
> This text (no link), I'll assume was that which was commented on by
> Peter in May, after the last working draft was published:
> 
>   [[4/ The constraint on only one rdf:ID (or rdf:bagID) for a URI in a given
>    document is hidden deep in the document.  It would be much better to
>    gather all these context-sensitive constraints in one place.  It would
>    be even much better to remove these context-sensitive constraints, as
>    there is no need to have only one rdf:ID with a particular URI in a
>    document.  The development of this constraint is rather confusing, as
>    there have been statements to the effect that rdf:about="#foo" is a
>    synonym for rdf:ID="foo".
>   ]] -- http://lists.w3.org/Archives/Public/www-rdf-comments/2002AprJun/0100.html
> 
> I responded to him and agreed to make changes:
> 
>   [[ Linking and making these constraints more prominent is a good
>      idea; I will add this.
> 
>      If I recall correctly, RDF Core decided that keeping them (for
>      IDs) was useful for users who could then rely on them, for
>      example, when defining RDF Schema RDF/XML documents, that the
>      terms being defined using rdf:ID were unique identifiers in that
>      RDF/XML file.
> 
>      It is true that the constraints don't apply when using
>      rdf:about="#foo" which I guess is seen more as referring rather
>      than defining "foo" despite these being equivalent; rather
>      rdf:ID="foo" is equivalent to rdf:about="#foo" but with the
>      extra constraint.
>   ]] -- http://lists.w3.org/Archives/Public/www-rdf-comments/2002AprJun/0119.html
> 
> All this is recorded in the changes section of the editors draft of
> the syntax WD as:
> 
> [[Update after comments by Patel-Schneider, 2002-05-21 outlined in
>   response 1 and response 2.
>   ...
>   Section 5.4 Constraints - added and moved the rdf:ID and rdf:bagID
>   constraints there linked from the old location in the grammar. 
>   ...
> ]]
> -- http://ilrt.org/discovery/2001/07/rdf-syntax-grammar/#section-Changes
> 
> The new section 5.4 is:
>   http://ilrt.org/discovery/2001/07/rdf-syntax-grammar/#section-constraints
> 
> with the test cases directly linked there.
> 
> Dave

I was guilty of looking at the WD not the editor's copy, so my comments are
not accurate.

That said, I still think that the text is very hard to comprehend.
Something like:

	A name can be used at most once as the value of an rdf:ID or
	rdf:bagID ...

would be much better.  Also, referring to the negative test case would
be better than referring to a positive test case.

peter
Received on Wednesday, 30 October 2002 07:13:58 GMT

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