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RE: Subtyping in XML

• To: "'Paul Prescod'" <paul@p...>,<xml-dev@l...>
• Subject: RE: Subtyping in XML
• From: "Aaron Skonnard" <aarons@d...>
• Date: Wed, 4 Sep 2002 08:28:05 -0600
• Importance: Normal
• In-reply-to: <3D74386E.5810EA14@p...>

Paul Prescod wrote:
 
>  * http://lists.xml.org/archives/xml-dev/200206/msg00265.html
> 
> So basically he's saying that it isn't safe to allow the data provider
> to nominate a schema that uses inheritance to extend your schema. If
you
> can't do that, then XML Schema inheritance is not really a mechanism
for
> improving the extensibility in XML. And XML's dirty little secret is
> that it isn't really that great at extensibility after all.
"Extending"
> a document type can break applications which is more or less what
> happens in binary formats too!

Type inheritance in XML Schema can provide extensibility benefits to the
author of the original schema. Such extensibility can be used to create
more flexible systems that support a wider range of input, and to solve
such problems as versioning, without overly complicating the code
(especially if the processing language is OO). And as Henry suggests,
the author of the schema (and the processing system) is in control of
the schema and defines all possible types accepted.

-aaron

......................................................
. Aaron Skonnard, DevelopMentor (http://skonnard.com).
.  Essential XML Quick Reference available online!   .
.    Download PDFs: http://www.develop.com/books     .
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• References:
  • Subtyping in XML
    • From: Paul Prescod <paul@p...>

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