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Re: How to Version XML Applications

From: Norman Walsh <Norman.Walsh@Sun.COM>
Date: Mon, 16 Sep 2002 11:06:07 -0400
To: www-tag@w3.org
Message-ID: <873csavusg.fsf@nwalsh.com>

/ "Anthony B. Coates" <abcoates@TheOffice.net> was heard to say:
|> To those applications, if you change the namespace name, you haven't
|> changed the namespace of the vocabulary, you've *changed the
|> vocabulary* by definition.
|
| You change the definition in principle, but not necessarily in practice.  Not
| that I would argue for versioned namespace URIs, but from an application
| developer's point of view, detecting the versioned namespace URI and loading the
| appropriate module for processing that version is no different to dealing with
| other versioning situations.

I think it is different. You can't develop an application that will
know what the "next version" URI will be, so your application of today
can't be programmed to "do the right thing" with some future version.

Take XSL again as an example. XSLT 1.0 processors know what to do with
an XSLT stylesheet that is marked "version='2.0'" (or version='10.0'
for that matter). They can be programmed with this behavior because
the namespace name of the elements isn't going to change (they'll
still recognize xsl:stylesheet).

I suppose you could do this with namespace names, if you introduced
some structured convention for the URIs. But I think that would be
wrong. (Because it would require applications to have another
microparser and structured attribute values are wrong.)

| so it should not be
| assumed that namespace versioning will die out via a process of natural
| selection.

No, I don't think that at all. And I think for some applications and
some sorts of version changes (as Noah has suggested), changing the
URI may be exactly the right choice. But it's a pretty disruptive
choice; more disruptive than necessary in many cases, I expect.

                                        Be seeing you,
                                          norm

-- 
Norman.Walsh@Sun.COM    | Waste no more time arguing what a good man
XML Standards Architect | should be. Be one.--Marcus Aurelius
Sun Microsystems, Inc.  | 
Received on Monday, 16 September 2002 11:07:01 GMT

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