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Re: xsi:schemaVersion

From: <noah_mendelsohn@us.ibm.com>
Date: Fri, 13 Sep 2002 10:27:56 -0400
To: "Dan Chang" <dtchang@us.ibm.com>
Cc: www-xml-schema-comments@w3.org
Message-ID: <OF3906B83C.9CDAFDAF-ON85256C33.004F1572@lotus.com>

Dan:

There's coincidently a discussion of XML versioning springing up on the 
Tag mailing list (TAG is essentially W3C's architectural steering 
committee).  See [1].  For my own opinions, see a posting I made in that 
thread last night [2]. 

You specifically suggest:

>> For this to be useful, I would like to
>> suggest that an xsi:schemaVersion be 
>> defined for use in an XML document to
>> provide hints as to the version(s) of a 
>> schema that may be used for
>> assessment.

I think this implies some assumptions about how schemas for different 
versions are somehow registered so a processor could "find them".  The 
usual way for finding things on the Web is URIs, and we'd have to be 
careful that a schemaVersion wasn't effectively a non-URI based mechanism 
for naming or searching for schema documents. 

As it stands, the schema recommendation gives nearly total flexibility to 
processors to find schemas in any manner desired, and new attributes are 
allowed on schema document constructions, so it seems that certain 
solutions could be implemented without changing the schema recommendation 
itself.  They could be published as additional conventions to be agreed 
upon and followed by processors.  Like Tim Bray (see thread referenced 
below), I think this is a very hard problem and to be approached with some 
caution.  I do agree it is important.  For the moment,further discussion 
should probably be on the TAG list (note, however, that the TAG strongly 
discourages rambling or repetitive discussions:  the idea there is not to 
drill this into the ground, but just to help the TAG decide whether to 
take any initiatives in this area.)  Thanks.

Thanks.

[1] http://lists.w3.org/Archives/Public/www-tag/2002Sep/0082.html
[2] http://lists.w3.org/Archives/Public/www-tag/2002Sep/0106.html

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Noah Mendelsohn                              Voice: 1-617-693-4036
IBM Corporation                                Fax: 1-617-693-8676
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Received on Friday, 13 September 2002 10:29:45 GMT

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