Andrew Welch wrote 
> use a version attribute to distinguish the versions

Where? 

The issue was that elements with the same name were defined differently in
both GML 2.0 and GML 3.0, 
But they had the same target namespace. The differences were subtle -
technical rather than conceptual - but real as far as a validating processor
is concerned. The XML namespace is to all practical intents and purposes the
designated identifier for 'the schema' and we had the same identifier for
different things. Chaos ensues. 


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Simon Cox

European Commission, Joint Research Centre, 
Institute for Environment and Sustainability, 
Spatial Data Infrastructures Unit, TP 262 
Via E. Fermi, 2749, I-21027 Ispra (VA), Italy 
Tel: +39 0332 78 3652
Fax: +39 0332 78 6325
mailto:simon.cox@j... 
http://ies.jrc.ec.europa.eu/simon-cox 

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-----Original Message-----
From: xmlschema-dev-request@w... [mailto:xmlschema-dev-request@w...] On
Behalf Of Andrew Welch
Sent: Wednesday, 2 September 2009 17:54
To: Simon Cox
Cc: noah_mendelsohn@u...; Tsao, Scott; G. Ken Holman; Henry S.
Thompson; xmlschema-dev@w...; ekimber
Subject: Re: Best Practices for Establishing Namespace Name

2009/9/2 Simon Cox <simon.cox@j...>:
> In some situations it is good to include dates or version numbers in 
> namespace names.
> For example, if your maintenance/governance arrangement expects new 
> versions, and particularly if the new versions are not compatible with 
> older versions.
> Geography Markup Language from OGC made the mistake of keeping the 
> same XML namespace for several incompatible versions of GML, and this 
> has caused confusion. (The policy has since been fixed).
>
> Of course, you can choose to give your new version a completely new 
> name and namespace, but sometimes you want to claim continuity, or at 
> least a common scope, with an earlier product, but not confuse 
> processors by having incompatible declarations in the same target
namesapce.

Interesting, I would still be tempted to keep the same namespace and use a
version attribute to distinguish the versions.  If those versions are
"compatible" or not doesn't really matter at the data level, all you need to
be able to do is differentiate your elements from others with the same local
name, and differentiate the versions.

In "GML", where do you think the confusion came from?  Unless they also
changed the prefix between versions, looking at snippets of markup you would
still be none the wiser.



--
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/