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[Bug 11125] Regex grammar for 1.1 renders some 1.0 regexes invalid

From: <bugzilla@jessica.w3.org>
Date: Sat, 23 Oct 2010 01:45:20 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1P9TAe-0002ji-7F@jessica.w3.org>

Dave Peterson <davep@iit.edu> changed:

           What    |Removed                     |Added
                 CC|                            |davep@iit.edu

--- Comment #2 from Dave Peterson <davep@iit.edu> 2010-10-23 01:45:19 UTC ---
(In reply to comment #0)
> From the telcon 2010-10-22:

> <dezell> MK: won't change the grammar, only the prose following rule 81 in the
> grammar.

In some sense that prose is "part of the grammar"; had the productions and
related material been updated to the format used in the other parts of 1.1,
prose like this would be in a formal Constraint, referenced from the production
display.  I like that format; it makes the intent clearer.  

> <dezell> MSM: I think we need a story about the topic in the Note, about what
> happens with more than one hyphen.
> <dezell> MK: we could change the rule to say if you can't parse as part of a
> character range then backtrack.

We already require lookahead (which is after all a form of backtrack) to see if
the next character following a '-' is '['; it shouldn't be any worse to also
lookahead to check if the next character is ']'.

(In reply to comment #1)
> I asserted during the telcon that the rules for 1.0 second edition were
> unclear, and Dave Petersen disputed this.

Let me be clear:  I only felt that the 2E rules were clear about the case we
are concerned with here, namely "Is '[+-]' legal?"  I have no certainty that
the 2E rules prevented ambiguities.

Beyond that, I concur with the changes Mike Kay has suggested above.  But I
hope someone succeeds in double-checking that they don't introduce problems
with other areas of the RE chapter.  (How do you prove a negative?)

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Received on Saturday, 23 October 2010 01:45:21 UTC

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