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Re: XML Schema working with DTDs?

From: Dan Connolly <connolly@w3.org>
Date: Sat, 29 Apr 2000 09:27:15 -0500
Message-ID: <390AF143.74BE6ED6@w3.org>
To: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
CC: Noah_Mendelsohn@lotus.com, cmsmcq@acm.org, reagle@w3.org, www-xml-schema-comments@w3.org
"Henry S. Thompson" wrote:
> I'll make three observations:
> 1) In the nicest possible way, I'm not sure what we owe to Joseph on
> this one.  We have _not_ published this namespace yet, in the sense of
> asserting publicly in a process-blessed way that
> http://www.w3.org/1999/XMLSchema is the namespace URI for a namespace
> whose semantics are defined in some officially approved REC.

While it's true that we're not 100% bound to support old drafts,
I hope that the spec will gradually stabilize; i.e. that we'll
gradually make more of an attempt to avoid problems like the
ones Joseph ran into.

> 2) The thrust of Dan's remarks are at odds with my memory of the
> discussions surrounding the decision to enforce
> http://www.w3.org/1999/XSL/Transform as the namespace URI for XSLT,
> which strongly suggested a philosophical stance about persistent
> identity clearly at odds with the practical reality of changing
> details.  In particular the decision to _not_ add a version number to
> that NS URI was taken after considerable thought.

I'm not sure what you mean by "enforce", but perhaps that's no matter...

My remarks aren't at odds with the way the XSLT namespace works;
they just don't apply. The XSL WG decided not to promise that the XSLT
namespace won't change. I think they made some promise about never
changing the namespace is such a way that would change the semantics
of a stylesheet that conforms to XSLT 1.0, but they left open
the possibility of backward-compatible changes to the namespace
(where "backwards-compatible change" is not formally specified).

I have not said that every namespace resource must be immutable.
I have just said that using immutable resources as namespaces
has some desireable characteristics, including avoiding
the "that schema just changed out from under me" problem
that Joseph ran into.

> I'm afraid this takes us back to my concern about too-tight connection
> between namespace URI and presumed resource (= XML Schema in this
> case) location.

In any particular way? Or just general unease?

> 3) There's certainly precedent for 'stable' resources evolving:  the
> XML Spec DTD still lives at http://www.w3.org/XML/1998/06/ although
> it's currently in its 21st edition.

I'm not sure what you mean by 'stable'. That resource isn't "stable
in the Ted Nelson sense; it changes whenever Eve feels like it.
Contrast that with
which are guaranteed by their publishers not to change, or
which is guaranteed by the definition of the URI scheme not to change.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Saturday, 29 April 2000 10:28:05 UTC

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