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Formulate erratum text on versioning for the web architecture document

From: John Kemp <john.kemp@nokia.com>
Date: Tue, 17 Feb 2009 10:46:38 -0500
Message-Id: <9744C470-FFC1-40AF-88D4-B4ECECD12180@nokia.com>
To: "www-tag@w3.org WG" <www-tag@w3.org>
Hello,

I acquired an action item [1] to investigate whether the AWWW best  
practice on versioning [2] should be updated in light of the  
versioning work done  by the TAG. Noah wrote a nice description of the  
issue on the TAG blog [3] which includes links to the relevant work  
done by Dave Orchard on versioning.

The AWWW currently says this, marked as a best practice:

  "A data format specification SHOULD provide for version information."

My understanding of that line is that when designing a data format  
specification, the author should provide a mechanism allowing an  
instance document, conforming to the said specification, to carry  
information pertaining to the version of the specified format with  
which the instance complies (where complies _might_ mean 'should  
validate against the related XML schema' or something else, at the  
specified discretion of the author). Of course, using XML namespaces  
in an appropriate manner would be one way by which this best practice  
could be applied.

As Noah described in [3], it is not always necessary for a format  
author to create an updated version identifier, or require its use in  
compliant instances. This particular item is also touched on in the  
AWWW in a section on Versioning and XML Namespace Policy [4]

I believe that the best practice is still correct and important - data  
format specifications should provide a mechanism (where that mechanism  
might simply be "use XML namespaces") allowing instances to indicate  
version information. Authors will likely not know whether they will  
later have to create a new, incompatible version of a format a priori,  
but should likely assume that they will.

I would suggest, however, that perhaps an additional best practice  
might be warranted, along the lines of Noah's suggestion in [3]:

  "If a language, or data format, changes in incompatible ways, a new  
version identifier should be assigned to the updated data format, and  
allowed in document instances."

Regards,

- johnk

[1] http://www.w3.org/2001/tag/group/track/actions/165
[2] http://www.w3.org/TR/webarch/#ext-version
[3] http://www.w3.org/QA/2007/12/version_identifiers_reconsider.html
[4] http://www.w3.org/TR/webarch/#versioning-xmlns
Received on Tuesday, 17 February 2009 15:49:27 GMT

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