RE: [xml-dev] Caution using XML Schema backward- or forward-compatibilit

[noah_mendelsohn@us.ibm.com]

David Carver wrote:

> That reason for extensibility is only necessary if the 
> central authority can't or won't respond quicker. ...
> organizations.   I wrote about this back in December of 2006. 
> Basically the central authority needs to adapt faster to 
> their members chaning needs:

Mike Kay wrote:

> All true...

Actually, I'm not convinced that's always the reason.  In many cases, the 
reason you want extensibility is that some core format or business 
document is to be extensible in different ways by different organization. 
So, an entire industry might agree on an extensible invoice or purchase 
order format, with the understanding that individual organizations using 
the document can add their own additional tracking fields and the like. In 
such cases, it would be inappropriate to try and route all the private 
extensions through a central authority, no matter how quick and responsive 
that authority is. 

One of the important dimensions to consider is that some XML languages 
are, for good reasons, evolved completely centrally.  Others are evolved 
by a limited number of organizations, sometimes in cooperation, but 
sometimes in competition.  It's not at all unusual for one organization to 
pick up a programming language, document format, etc., to change it, 
perhaps in compatible ways or perhaps in other ways, and to promote the 
use of its version(s) in competition with others that are out there.  This 
certainly happened with HTML for quite awhile.  Finally, as mentioend 
above, some languages are intended from the start for decentralized 
enhancement or evolution.  In many cases, those languages prove to be some 
of the most interesting and powerful for users.

Noah

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Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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