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Re: xml-stylesheet issues--suggested resolutions

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Tue, 16 Jun 2009 17:09:55 +0100
To: "Simon Pieters" <simonp@opera.com>
Cc: "Grosso, Paul" <pgrosso@ptc.com>, public-xml-core-wg@w3.org
Message-ID: <f5b4ougp3cc.fsf@hildegard.inf.ed.ac.uk>
Hash: SHA1

Simon wrote
> Paul wrote
>> Simon wrote
>>> * What happens when the PI is XML 1.0-well-formed but doesn't
>>> follow the xml-stylesheet syntax?
>>> * What happens when there are duplicate pseudo-attributes?  (This
>>> seems to actually be allowed in the syntax.)
>>I suggest:
>> This is an error; the xml-stylesheet processor MAY ignore the
>> entire PI; if it tries to recover, it SHOULD ignore all but the
>> last assignment to a given pseudo-attribute.

> I doubt there is enough legacy content with invalid xml-stylesheet PIs
> to  make browser vendors ignore the spec. I say this because there are
> surprisingly few bugs reported on Opera for our Draconian handling of
> invalid xml-stylesheet PIs.

>> In this duplicate pseudo-attribute case, I could live with
>> tightening my above suggestion to "...processor SHOULD ignore..."
>> because at least that way Arbortext could say "yes, we should,
>> but due to legacy issues, we decided instead to recover" and
>> still not be non-compliant with the spec.

> Is the legacy situation for Abortext so bad that people rely on its
> error recovery behavior?

I agree that a) we're unlikely to find anything even moderately
forceful that doesn't put some browsers or other processors on the
back foot; b) we are pretty much free to decide what's most correct
and useful here.

It's not obvious to me that interoperability is helped by disjunctive
MUST (or for that matter SHOULD) clauses.  I'm inclined to think that
we're not doing anyone any favours by defining a recovery behaviour in
the duplicate PA case.  So I'd propose

  Duplicate pseudo-attributes are an error.  The xml-stylesheet
  processor MUST process the xml-stylesheet as if none of the
  pseudo-attributes which share a name were present.

This will lead to user-useful behaviour in all cases except
duplication of the href PA, I think.

- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Tuesday, 16 June 2009 16:10:49 UTC

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