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Re: [xmlProfiles-29] TAG recommendation for work on subset of XML 1.1

From: Richard Tobin <richard@cogsci.ed.ac.uk>
Date: Thu, 6 Feb 2003 14:18:20 GMT
Message-Id: <200302061418.OAA27546@rhymer.cogsci.ed.ac.uk>
To: ht@cogsci.ed.ac.uk (Henry S. Thompson), www-tag@w3.org

> I am unconvinced of the necessity for subsetting the language, as
> opposed to identifying a new conformance class alongside the two
> already provided ('validating' and 'non-validating').
> Call such a conformance class 'minimal' -- it can be trivially defined
> as a further restriction of 'non-validating', as follows (this is an
> edited copy of text from section 5.1 of XML 1.0 2e [1], changes in
> bold):

I think the minimal conformance Henry describes is either too minimal
or not minimal enough.  It ignores all entity declarations, and
doesn't provide attribute defaults, but it still requires parsing
ATTLIST declarations to do attribute normalization.  If we allow
processors to ignore part of the internal subset, we might as well
allow them to ignore the whole thing so that they don't even have to
parse it.  Attribute normalization seems the least valuable of the
three since it can usually be handled in the application.

(Skipping the internal subset is just a few lines of code: you have to
watch out for comments and quoted literals.)

The choice between defining a subset and defining a conformance level
is a choice between two reductions in interoperability: we break
either the rule that all parsers can handle all documents, or the rule
that all parsers produce the same infoset for a given document.  Of
course, both these rules are already broken.  The first is broken by
unsupported encodings and URI schemes, the second by parsers that
don't read the external subset or external general entities.

-- Richard
Received on Thursday, 6 February 2003 09:18:26 UTC

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