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on Extending and Versioning draft findings

From: Dan Connolly <connolly@w3.org>
Date: Mon, 24 Jan 2005 11:31:05 -0600
To: David Orchard <David.Orchard@BEA.com>, Norman Walsh <Norman.Walsh@Sun.COM>
Cc: www-tag@w3.org
Message-Id: <1106587865.5075.29.camel@localhost>

On the way back from Helsinki, I looked at...

 [Editorial Draft] Extending and Versioning XML Languages Part 1
 Draft TAG Finding 24 November 2004


I'm still not sure what the scope of the finding is trying to be; the
title suggests XML languages, but then I read:

  This finding describes techniques to achieve more effective loose
  coupling between systems by providing a means for backwards-
  and forwards-compatible changes to occur when systems evolve.

The core definition seems to be

 [Definition: Extensible if instances of the language can include terms
from other vocabularies.]

but I'm having trouble understanding it. "other vocabularies" suggests
that each language has one vocabulary. The UML diagram (if I read
it correctly) says that the relationship of languages to vocabularies
is 1 to many. I don't understand what "other vocabularies" means
in that case.

Perhaps the core definition is

 [Definition: A language change is backwards compatible if newer
processors can process all instances of the old language. ]

I infer that processor is a synonym for 'receiver', though I wonder
why other synonyms were identified and that one was not. Hmm...
the text actually defines the terms 'producer' and 'consumer'.
I'm getting confused. And it's not clear to me that cat(1) is
not a receiver for all languages, and hence all language
changes are backwards compatible.

Maybe these definitions aren't supposed to be the main focus
of this draft, but they're right there at the start, without
any motivating examples to study first. If the definitions
aren't supposed to be central, please move them to a less
central position in the draft; an "in progress" appending
or some such.

  [Editorial Draft] Extending and Versioning XML Languages Part 2:
Schema Languages
  Draft TAG Finding 24 November 2004


I note "It is heavily XML schema based, but only because of scheduling.
OWL/RDF and RelaxNG sections wil be added" which makes me think perhaps
I should have waited until those sections were added to commit
to a review. But pressing on...

"Re-use namespace names Rule: If a backwards compatible change can be
made to a specification, then the old namespace name SHOULD be used in
conjunction with XML_s extensibility model"

That GPN should say "if you're constrained to use XML Schema..." yes?

And what does "XML_s extensibility model" refer to? Maybe I'm reading
too fast?

for reference:

ACTION DC: to review parts 1 and 2 of extensibility and versioning
editorial draft finding

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Monday, 24 January 2005 17:31:07 UTC

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