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Re: How to Version XML Applications

From: Tim Bray <tbray@textuality.com>
Date: Wed, 11 Sep 2002 15:04:06 -0700
Message-ID: <3D7FBDD6.8030402@textuality.com>
To: "Anthony B. Coates" <abcoates@TheOffice.net>
Cc: www-tag <www-tag@w3.org>

Anthony B. Coates wrote:

> To follow on from a couple of the other replies, the "self-describing" view
> currently fails because W3C XML Schema doesn't support it.  The great unwashed
> just go by what the Schema spec allows.  If TAG could co-erce the W3C XML Schema
> WG into introducing a "schemaVersion" attribute which Schema processors are
> required to respect, that would go a long way towards clearing up this problem.
> Much as it would be nice to have a less invasive solution, I cannot think of one.
> Can anybody else?

Wrong.  There is not a one-to-one relationship between languages and 
schemas.  I could rev a language by changing the semantic descriptions 
of how its elements ought to be rendered, without changing the syntax 
constraints expressed in the schema.  I could rev the schema because 
it's hard to read or needs to be re-modularized or validation runs slow, 
without effectively changing the language.

What Norm's talking about is, I think, a compulsory version attribute on 
the root element that describes the version of the *language*; whichever 
schema you happen to use should require the presence of this attribute. 
  This does indeed make the language self-describing in at least the 
version number of instances.  -Tim
Received on Wednesday, 11 September 2002 18:04:04 GMT

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