[Resend, now that I can post again!]
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Message-ID: <3607E3EE.FDD1155A@eng.sun.com>
Date: Tue, 22 Sep 1998 10:52:46 -0700
From: David Brownell <db@eng.sun.com>
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To: xml-dev@ic.ac.uk
Subject: Re: namespaces for name attribute values?
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Andrew Layman wrote:
>
> Perhaps you do not really have a problem. What I'm thinking is that if you
> wrote something similar to the example you showed,
>
> <foo xmlns:DC="http://purl.org/metadata/dublin_core">
> <DC:Creator>Eric Hellman</DC:Creator>
> </foo>
>
> then the meaning of DC:Creator is not affected by any additions made to
> Dublin Core. Your DTD remains valid, simply not as extensive as the
> (expanded) Dublin Core.
For Dublin Core, perhaps -- but not in general. Suppose
the addition were to modify the content model for something
like the "Creator" element referred to above? Validity isn't
automatically preserved in such cases.
Namespaces need versioning. URIs can easily include date
codes like "02Nov1997"; W3C itself uses such a scheme, as
you can see by looking at versions of the namespace spec.
I'd expect the definers of such namespaces to identify
their versioning policy, including publishing URLs which
apply to each iteration. A "most current" URL can be of
use in some cases (loose coupling), but not usually in
systems that depend on precise semantics and hence need
updates to support new features.
So my response to Eric is to get a versioned URL for the
Dublin Core, and to use that! ;-)
- Dave
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