[whatwg] "must only" ambiguity

[Krzysztof Żelechowski]

Dnia 24-12-2007, Pn o godzinie 16:36 -0500, L. David Baron pisze:
> On Monday 2007-12-24 19:07 +0100, Krzysztof Żelechowski wrote:
> > My rewording for competition: 
> > "Authors may use elements in the HTML namespace 
> > in the contexts where they are explicitly allowed and nowhere else."
> 
> > My rewording for competition: 
> > "Authors may put elements inside an element only if that element..."
> > (because "only if" is a common and well understood expression.)
> 
> These won't work because they make the statement a much weaker
> requirement per RFC 2119:
> http://www.ietf.org/rfc/rfc2119.txt
> 
> Changing from a MUST or MUST NOT to a MAY is a substantive change,
> not a rewording.

RFC 2119 does not forbid using MAY conditionally.  Under these
conditions, this is a MAY, otherwise this is a MUST-NOT.  If you prefer
MUST NOT to MAY NOT, which is about the same in English, you can say
"... and MUST NOT use them anywhere else."

Note that this is a true MAY, not a MUST; you NEED NOT use any HTML
elements at all, except for a few that make the basic skeleton of a
document, and I may even be wrong here because those elements may be
supplied by the user agent so that an empty document is a valid
document; but that MUST is described elsewhere, and I may even be wrong
here because those elements may be supplied by the user agent so that an
empty document can be treated as valid.

Chris