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Re: summary of reification semantics issues (material for discus sion).

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Mon, 24 Mar 2003 15:57:31 +0000
Message-Id: <5.1.0.14.0.20030324152214.00b05de0@localhost>
To: Tim Berners-Lee <timbl@w3.org>
Cc: pat hayes <phayes@ai.uwf.edu>, Graham Klyne <GK@NineByNine.org>, Frank Manola <fmanola@mitre.org>, RDF Core <w3c-rdfcore-wg@w3.org>

Tim,

 From your response, it is clear that there is still more work to do to 
help you understand the WG's position, but perhaps it is time to cut to the 
chase.

At 00:45 24/03/2003 +0000, Tim Berners-Lee wrote:

[...]


>Yes... the only logical thing is to remove it, and it would be easier
>earlier than later, but would involve of course changing RDF M&S.

This is the question that is at the heart of the judgement call the WG had 
to make.  Leaving aside the question of charter, should the WG pull 
reification entirely?

People are using it.  If reification is withdrawn, that use is rendered 
non-conformant.  There is nothing currently to replace the 
functionality.  We are weighing that against the difficulties that 
reification causes.

We could take on the issue and propose a 'proper' solution.  But this is 
not a simple problem space.  You talk as if 'quoting' were a simple thing, 
but there are different forms of quoting and we ought to understand how 
they relate to contexts and the like before picking a solution.  We have 
already established that the current vocabulary is inadequate for the form 
of quoting you desire (handling b-nodes and the difference between a URI 
and a literal).  We would have to consider not only the use cases you have 
in cwm, but also the original motivation - provenance - which takes us into 
the triples or quads discussion.

This is not easy.  RDFCore has been running for two years - I suggest it 
needs to finish what its got before it embarks on exploring those murky 
waters.  So proposing an alternative reification solution is not an option.

Which leaves us with a choice between:

   - withdraw the reification vocabulary, leave nothing in its place for a 
while and render those
     who use the current vocabulary non-conformant

   - reduce the prominence of the current vocabulary, but leave it in place 
for those who are
     using it, and clarify its specification

Might you be persuaded that in these circumstances, the best course of 
action is to leave it to a new, fresher WG to consider these issues and 
that that WG would be best placed to decide how to move current use to 
whatever solution they propose.

In the meantime, the best strategy for the current WG is to reduce the 
prominence of the existing vocabulary, whilst at the same time clarifying 
its specification for those who have chosen to use it.

Brian
Received on Monday, 24 March 2003 10:56:59 EST

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