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PSVI issues

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 08 May 2008 14:11:47 +0100
To: public-xml-processing-model-wg@w3.org
Message-ID: <f5br6cdym7g.fsf@hildegard.inf.ed.ac.uk>

Hash: SHA1

1) The functionality provided by the 'psvi-required' attribute is
   perfectly reasonable and self-contained, and it should be retained
   unchanged.  If I want to write pipelines which simple won't work
   (statically) when a processor doesn't support the PSVI, that's what
   I'll use.

2) I am unconvinced that we need to provide a means to tell processors
   which do support the PSVI whether or not they need to do so when
   executing a particular pipeline.  That feels like an
   product-specific optimisation to me, and as such _finally_ gives me
   an example of a realistic use for <pipeinfo> -- a product is free
   do define a <pipeinfo> child which can be inserted before
   e.g. validate steps to say, in effect, "I do/don't care about the

   I'd rather wait until we see if such annotations turn out to be
   provided, and what they look like, before trying to add something
   along those lines into the language.

3) Having said that, I think it _does_ make sense to provide a means
   for pipeline authors to do something at runtime depending on PSVI
   support.  But I think the minimum necessary to declare victory is
   just psvi-available(), which if true means the processor claims
   it's passing PSVI information along.  No granularity or locality is
   implied, that is, the value should be the same at all times/places
   within a given episode.

4) Wrt to the amount of support required, I think we say PSVI support
   implies two things:

   a) All PSVI properties produced on the output of a step MUST be
      available to the steps which take that output as one of their

   b) Implementations SHOULD preserve PSVI properties across steps
      insofar as that is consistent with step semantics.  It is
      implementation-defined what PSVI properties it supports overall,
      and what PSVI properties are lost by what steps.

- -- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Thursday, 8 May 2008 13:12:20 UTC

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