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help needed with RDFS issue pfps-12, wellformedness of lists

From: Dan Brickley <danbri@w3.org>
Date: Fri, 25 Apr 2003 11:59:15 -0400
To: w3c-rdfcore-wg@w3.org
Message-ID: <20030425155915.GH12807@tux.w3.org>

http://www.w3.org/2001/sw/RDFCore/20030123-issues/#pfps-12
http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0160.html

[[
Summary:

The RDF Schema document

   http://www.w3.org/TR/rdf-schema/#ch_collectionvocab

describes lists as though they were always "well formed", which they are not.
]]


I can think of two ways of tackling this issue. Either a 'health warning' approach,
where we note that partial or broken rdf:List descriptions are possible, or by
trying to account for the rules for being a wellformed rdf:List. The latter was 
begun in the Peter/Brian dialog cited above:
[[
Brian:
> > A rdf:List is well formed if it meets either of the following conditions:
> >
> >    o it is rdf:nil
> >    o - it has exactly one rdf:first property,
> >      - and it has one rdf:rest property
> >      - and the value of its rdf:rest property is a well formed list.

Peter:
>This is not sufficient to describe well-formed lists!  (Think of infinite
>or circular lists.  Also think of what happens if rdf:nil is the subject of
>a triple whose predicate is rdf:first or rdf:rest.)

Brian:
Just so.

Right, I think we've got the point where we have clarified what the issue 
is, but we are probably going to have to think a little more about how best 
to address it.
]]

I need help in progressing this towards an issue closure proposal. Could someone
take a crack at refining the above exchange into a more solid 
characterisation of rdf:List? Especially re the circular and infinite concerns 
Peter raises.

Perhaps we should also write, "An RDF description of a rdf:List is well formed"
rather than "A rdf:List is well formed..."?

Dan
Received on Friday, 25 April 2003 11:59:16 EDT

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