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Re: C.7 inclusions and exclusions?

From: Arjun Ray <aray@nmds.com>
Date: Fri, 18 Oct 1996 21:43:26 -0400
Message-Id: <>
To: W3C SGML Working Group <w3c-sgml-wg@w3.org>
At 01:21 PM 10/17/96 CDT, Michael Sperberg-McQueen wrote:

>C.7 Should XML prohibit the use of inclusion and exclusion exceptions
>in element declarations? (11.2.4, 11.2.5)?


There is no impact on DTD-less parsing either way (OK, OK, I'm aware of the
RS/RE complications and sundry other esoterica, but the operative assumption
is that those gotchas will be resolved adequately.)

It's a validation issue. I see no reason to require that a validator be a
parser, so the considerations reduce to 
  (a) whether the presence of inclusions and exclusions make the recognition
problem inherently more difficult for implementors, and 
  (b) whether the absence of inclusions and exclusions make the structure
definition problem inherently more difficult for users.

Ad a) the difficulties for parsers stem from inclusions and exclusions being
shorthand for an otherwise factorially larger set of rules. But I'm not
convinced that this is a show-stopper for recognizers.

Ad b) given that users will find the need for floating elements and to
prohibit (indirect) recursion, the utility of inclusions and exclusions
shouldn't be in doubt.

So it boils down to whether the technical reasons to prohibit them are
sufficiently severe.



Received on Friday, 18 October 1996 21:41:49 UTC

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