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Re: DTD Fragments and XML

From: David Durand <dgd@cs.bu.edu>
Date: Sun, 4 May 1997 12:26:55 -0500
Message-Id: <v03007801af9275a041ab@[]>
To: w3c-sgml-wg@w3.org
At 9:09 AM -0700 5/3/97, Terry Allen wrote:
>| I don't think that we can make it easy to combine DTDs without changing
>| SGML. But maybe we can figure out a way to declare a namespace for
>| elements: to "import" element names in a standard way. You wouldn't be
>| able to validate the document but at least it would be clear what the
>| elements MEAN.
>A universal typology of human knowledge would do that for you, but
>there will never be one.  All you can do is refer to well known
>external semantics, e.g., via fixed attributes.  This is not an
>XML issue; the problem is the same in SGML.

My proposal, long ago, that we allow "addition" of an element into a
content model solves this problem, without a universal taxonomy of
knowledge, but simply a more flexible DTD language. The concrete proposal
was to allow the extension of content models of the (x | y | z)* form by a
declaration that an element "mixes-into" the content of another element.

   I'm not suggesting that we revisit this -- We decided that we were not
going to extend/change the DTD language, for compatibility reasons. This
kind of capability is still a great opportunity for a markup-based DTD
creation application, but of course we will never have the end-user
extensibility that we  would get with an extended DTD language.

   Note that all the facilities one would gain with such a feature can be
implemented via parameter entities....

   An observation...
   -- David

David Durand              dgd@cs.bu.edu  \  david@dynamicDiagrams.com
Boston University Computer Science        \  Sr. Analyst
http://www.cs.bu.edu/students/grads/dgd/   \  Dynamic Diagrams
--------------------------------------------\  http://dynamicDiagrams.com/
MAPA: mapping for the WWW                    \__________________________
Received on Sunday, 4 May 1997 14:04:31 UTC

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