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Re: Changing Namespaces Between Specification Versions (was: XI

• From: "Pete Cordell" <petexmldev@c...>
• To: "Michael Kay" <mike@s...>,"'Paul Spencer'" <xml-dev-list@b...>,"'xml-dev'" <xml-dev@l...>
• Date: Wed, 22 Apr 2009 11:08:14 +0100

I concur with Michael's observation, but I don't think a version attribute 
alone is sufficient for good versioning.  My experience is that a versioning 
strategy doesn't happen by chance, and it needs to be thought about when 
version 1 is being developed; something that doesn't always happen.

I prefer something like a 'require' attribute in the root element that 
contains a list of constants (or URIs) of what a receiving node must 
understand in order to process a message.  For example the attribute may be 
something like require="foo bar baz".  It keeps all the feature negotiation 
in one place, and makes it easy for the receiving node to report back that, 
for example, it does not understand 'bar'.

(I know this wasn't the question, but since versioning seems to be so badly 
catered for I thought a little extra on it in web-o-sphere wouldn't hurt!)

Regards,

Pete Cordell
Codalogic Ltd
Interface XML to C++ the easy way using XML C++
data binding to convert XSD schemas to C++ classes.
Visit http://codalogic.com/lmx/ for more info

----- Original Message ----- 
From: "Michael Kay" <mike@s...>
To: "'Paul Spencer'" <xml-dev-list@b...>; "'Liam Quin'" 
<liam@w...>; "'xml-dev'" <xml-dev@l...>
Sent: Tuesday, April 21, 2009 2:20 PM
Subject: RE: Changing Namespaces Between Specification Versions 
(was: XIN: XML implicit namespace definitions)


>
>> Many people do change namespaces between versions. I prefer
>> not to, but have been persuaded to allow it in the past,
>> where the argument has been that the meaning of a name has
>> changed, so the namespace should change as well.
>>
>> Michael, what are your reasons for not doing this?
>>
>
> You want to design things so that transition from one version to the next 
> is
> as smooth as possible. Changing the names of 1000 elements because one of
> them has changed its meaning ever so slightly is not a good tradeoff -
> everyone who has written code to access the other 999 elements is going to
> have to change their code. A version attribute is so much less disruptive.
>
> Michael Kay
> http://www.saxonica.com/
>
>
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• Follow-Ups:
  • RE: Changing Namespaces Between Specification Versions (was: XIN: XML implicit namespace definitions)
    • From: "Michael Kay" <mike@s...>

• References:
  • Changing Namespaces Between Specification Versions (was: XIN: XML implicit namespace definitions)
    • From: "Paul Spencer" <xml-dev-list@b...>
  • RE: Changing Namespaces Between Specification Versions (was: XIN: XML implicit namespace definitions)
    • From: "Michael Kay" <mike@s...>