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Re: support for substitution groups, support for redefines?

From: Jeff Rafter <lists@jeffrafter.com>
Date: Thu, 07 Jul 2005 10:57:41 -0700
Message-ID: <42CD6D15.8020204@jeffrafter.com>
To: Bryan Rasmussen <brs@itst.dk>
CC: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>

> Does anyone have a good overview of how well substitution groups and
> redefines are supported in various processors. The last big project where I
> used redefines extensively about half a year ago I had to redo halfway
> through after running into too many problems, problems where the redefine
> was proper and was supported by some processors but failed in others, even
> more insidious where cases where I had redefined incorrectly and it
> functioned in some processors or in some test instances only to fail later.
> This has put me off redefines, now I'm on something where redefines and
> substitution groups are being proposed as the extensibility mechanism. I've
> had misgivings about substitution groups, finding them somewhat overly
> complicated and have thus avoided them. How is their support?


I recently ran through a series of tests on <redefine> in terms of 
validation and was very surprised at its portability. I too had played 
with it a year or two ago and found that support was lacking. I am only 
just getting into use in other tools like data binding and intellisense 
type applications-- so I haven't really tested that.

The only real interop problem I ran into was with <redefine>ing 
chameleon components into a schema with a target namespace. The behavior 
seemed consistent for simple examples. But when I tried to 
simultaneously redefine a chameleon component as it was being included 
in a schema with a targetNamespace and add attributes from another 
imported namespace the validator choked on the instances.

The results were good enough that I was able to recommend its use. I 
also did not test any forms of restriction-- which only compounds the issue.

Jeff Rafter
Received on Thursday, 7 July 2005 17:57:48 UTC

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