Re: Replacing ‘may not’ and ‘shall not’ by ‘must not‘ ?
On Wed, 26 Oct 2011 at 09:32:09 +1100, Ben Finney wrote:
> Charles Plessy <email@example.com> writes:
> > being a non-native speaker, I sometimes make the error of
> > understanding “may not” as “it is allowed to (one may) not do”, while
> > it rather means “must not”. Like for instance in the recent discussion
> > about dashes in version numbers on debian-mentors.
> There is a difference in nuance between “may not” versus “must not”.
> The former is simply the negation of “may”, and I think on that basis
> it's the correct form to use.
(I'm not a Policy maintainer, but I am a native en_GB speaker and an author
of specifications using RFC-like conventions...)
I think Charles is right that "may not" is more ambiguous: whether it's
correct or not, people do use "may not" to mean "might not", as in
"it may not work, you'll have to try it and see", whereas I've never seen
"must not" used wrong.
RFC 2119 doesn't define a meaning for "MAY NOT", presumably because of that
ambiguity. The scale from negative to positive in the RFC goes:
MUST NOT (= SHALL NOT)
SHOULD NOT (= NOT RECOMMENDED)
MAY (= OPTIONAL)
SHOULD (= RECOMMENDED)
MUST (= SHALL)