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Re: SD4 - Schema format

From: Robert Streich <streich@slb.com>
Date: Sat, 17 May 1997 04:02:01 -0500
Message-Id: <>
To: w3c-sgml-wg@w3.org
I didn't get a copy back from the list on this one, so I'm assuming a
failure at least since Paul obviously got a copy. My apologies if this
is a duplicate for you and the real failure was in the mail system on
my end.


I didn't believe there was a compelling technical reason for using
instance syntax for DTDs several months ago nor do any of the SDx
proposals change my opionion now. Whether you use instance syntax or
(current) DTD syntax, you have to hard-wire the DTD grammar into the

And I don't think that the argument that many of us already use instance
syntax for describing DTDs is valid either. The reason that we use
instance syntax for DTDs is because we want to keep marked up
documentation with the declarations. If SGML DTDs did use instance
syntax, we'd still have a "DTD for DTDs" of our own, for example.

In fact, proposals SD3-4 make me convinced that the only way to stay
on track is to simply create an XML application that describes schemata,
i.e., an XML DTD (current syntax) for creating schemata of all types,
one of which could be XML DTDs. However, just as other applications will
use a description of a schema to instantiate their own representation
in a format optimized for their own use, an XML schema should be
instantiated as an XML DTD. So we get a path like the one below:

			   XML DTD
		 ____\ for Schema Docs
		|    / (current syntax)
		|	       |
		|	       |
		|	      \ /
		|	 XML Instance
		|	of a Schema Doc
		|	       |
			      \ /
			    XML DTD
			 for Doctype X

I think that this is the only way we can address the issues of data
types, etc. in a meaningful way without having to rehash nearly everything
from square one. It would also allow us to discuss proposals such as
Henry's in a different light since we'd now be talking about how to
define the application (the XML DTD for Schema Docs) and not trying to
redefine DTDs.

Received on Saturday, 17 May 1997 04:03:48 UTC

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