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Microsoft's Namespaces Proposal (TAG ACTION-327)

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 19 Nov 2009 12:52:47 +0000
To: www-tag@w3.org
Message-ID: <f5bk4xmad7k.fsf@hildegard.inf.ed.ac.uk>
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Further to TAG ACTION-327: Review Microsoft's namespaces in HTML 5 
proposal, herewith a review.

I have read through this document [1] which was submitted as a change
proposal to the HTML Working Group against theirISSUE-41 [2].

Its opening section sets out the argument for distributed extensibly
succintly and well.

It goes on to present a core proposal, to support namespace
declarations for prefixes and prefixed element and attribute names,
plus a number of possible additions:

 1) to allow default namespace declarations with the expected effect
    on unprefixed element and attribute names, except that
    declarations on the document element are ignored (because they are
    in practice often broken XHTML namespace declarations);

 2) to treat unbound prefixes as if they were identity-declared,
    i.e. <udp:foo/> would be the equivalent of <udb:foo
    xmlns:udp="udp"/> if no declaration for 'udp' was in scope;

 3) to define short namespace names for commonly-used namespaces,
    e.g. 'html', 'svg', which could be used in declarations.

In my view the core proposal is sound, but does not address either of
the criticisms of the namespace mechanism which I understand as core
to the opposition to using it for distributed extensibility for HTML
5:

 a) Syntactic complexity;
 b) API complexity.

It also leaves unanswered some moderately important questions as
regards DOM construction, in particular whether 

 <x:div xmlns:x="http://www.w3.org/1999/xhtml">

results in an Element whose local name is 'div' or 'DIV'. 

I personally don't see any value in the last two options, since they
are a) not anything I'm aware of a demand for and b) would lead to
more, not less, API complexity.

The first option, regarding default namespace declaration and use, is
harder to assess: including it brings the proposal nearly in line with
Namespaces for XML, but the exception for the document element, while
pragmatically well-motivated, is messy and will I fear lead to more
confusion than value. . .

ht

[1] http://lists.w3.org/Archives/Public/public-html/2009Sep/att-1216/MicrosoftDistributedExtensibilitySubmission.htm
[2] http://www.w3.org/html/wg/tracker/issues/41
- -- 
       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/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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Received on Thursday, 19 November 2009 12:53:19 GMT

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