W3C home > Mailing lists > Public > public-xml-id@w3.org > January 2005

Re: 2. Effect of normalisation step on the DOM/Infoset

From: Ian Hickson <ian@hixie.ch>
Date: Thu, 20 Jan 2005 12:49:37 +0000 (UTC)
To: Norman Walsh <Norman.Walsh@Sun.COM>
Cc: public-xml-id@w3.org
Message-ID: <Pine.LNX.4.61.0501201247141.8099@dhalsim.dreamhost.com>

On Wed, 5 Jan 2005, Norman Walsh wrote:
> | | 4 Processing xml:id Attributes
> | |
> | | Each xml:id attribute is processed in the following way:
> |
> | It is unclear whether this processing is intended to change the DOM
> | (or the infoset, for that matter) or not. If one has the following
> | document:
> |
> |    <test xml:id=" test "/>
> |
> | ...what would be returned by:
> |
> |    document.documentElement.getAttributeNS('http://www.w3.org/XML/1998/namespace', 'id');
> |
> | Should it be " test " or "test"?
> |
> | I think it should be made clear that the processing mentioned in this
> | section is merely internal to the xml:id processor and does not affect
> | the infoset or the DOM. (This comment obviously doesn't apply to the
> | "ID Assignment" phase, where you definitely do want the infoset and
> | the DOM to be updated, but that's another matter.)
> 
> On the contrary, I think the purpose of attribute value normalization is
> so that down-stream processes will see the normalized value.

This causes a backwards-compatibility issue. A document processed by a 
DOM-aware XML processor will create a different DOM than one processed by 
a DOM-aware XML processor with XML ID support.

I think this is a very bad situation to be in. Scripts frequently trip 
over this kind of problem already, and I feel quite strongly that we 
should not make it worse.


> I think the result of processing your example with an xml:id Processor 
> should be the same as the result of processing this document with a 
> standard parser:
> 
> <!DOCTYPE test [
> <!ATTLIST test xml:id ID #IMPLIED>
> ]>
> <test xml:id=" test "/>

The difference being that such a document would always be processed that 
way, whereas xml:id introduces a new difference that not all XML 
processors will be aware of.

Thus I disagree with this resolution.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Thursday, 20 January 2005 12:49:38 UTC

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