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Appendix F says: "All XML characters are valid character ranges, except as follows:... The ^ character is only valid at the beginning of a positive character group if it is part of a negative character group; ...". However, the EBNF doesn't seem consistent with this. Consider [^X] This is ambiguous wrt the EBNF, since "^" is an XmlCharIncDash and thus a charRange: according to the EBNF it could be a powCharGroup containing "^" and "X" or a negCharGroup containing "X". Consider also [^] According to the EBNF, this is unambiguously a posCharGroup containing "^", but this is inconsistent with the prose. See: http://lists.w3.org/Archives/Public/www-xml-schema-comments/2002AprJun/0007.html
Note: R-134 was reopened at the Feb. 21 2003 telecon.
The WG classified this issue as a requirement at its telcon of 13 January 2006 and instructed the editors to prepare a proposal with the obvious fix.
At the face to face meeting of January 2006 in St. Petersburg, the Working Group decided not to take further action on this issue in XML Schema 1.1. (This issue was not discussed separately; it was one of those which were dispatched by a blanket decision that all other open issues would be closed without action, unless raised again in last-call comments.) Some members of the Working Group expressed regret over not being able to resolve all the issues dealt with in this way, but on the whole the Working Group felt it better not to delay Datatypes 1.1 in order to resolve all of them. This issue should have been marked as RESOLVED /WONTFIX at that time, but apparently was not. I am marking it that way now, to reduce confusion.
Since bug 1889 has been reopened, we should probably reopen all of the issues relating to the grammar of regular expressions, including this one.
A wording proposal intended to resolve this issue (and some other regex-related issues) is at http://www.w3.org/XML/Group/2004/06/xmlschema-2/datatypes.b1889.html (member-only link).
The wording proposal mentioned in comment #5 was adopted by the WG at its call today. We believe it resolves the issue in full, and I am accordingly marking the issue as resolved. At the publication of the next working draft, the originator of the comment (James Clark) should be notified and asked whether he believes the issue has at last been resolved satisfactorily.