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Re: Errata in section 2.4 of Extensible Markup Language (XML) 1.0 (Fifth Edition)

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Fri, 04 Nov 2011 14:21:30 +0000
To: Daniel van Vugt <vanvugt@gmail.com>
Cc: "Grosso, Paul" <pgrosso@ptc.com>, xml-editor@w3.org
Message-ID: <f5baa8c7ytx.fsf@calexico.inf.ed.ac.uk>
Daniel van Vugt writes:

> I am very surprised you are not accepting corrections to the standard,
> for mistakes that you acknowledge do exist. Especially a correction
> such as this which only requires changing a single character.

Sorry, not a mistake.  An ambiguous grammar defines a language just
fine.  Non-ambiguity is not a requirement.

> However, this is not the first time I have encountered an official
> language specification with BNF grammar where the authors have stated
> they don't guarantee the grammar to be technically accurate...

Again, "technically accurate" is not a defined term wrt context-free
grammars.  I'm not aware of any suggestion that saying a grammar is
expressed in BNF implies it is unambiguous.  the ambiguities you
identified are benign, in that they have no impact on the semantics of
the relevant expressions.

> For the benefit of the wider community, I think it would be helpful to
> still publish the errata, even indefinitely, and even if you have no
> intention of ever resolving the problems in the main document.

If we ever issue another edition, a Note to the effect that the
grammar represented by the BNF is ambiguous should be considered, I
agree.

ht
-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
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Received on Friday, 4 November 2011 14:24:41 GMT

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