Re: Exception to "MUST NOT"

["Jiwoong Lee" <porce at ktf.com>]

----- Original Message ----- 
From: "Harald Alvestrand" <harald at alvestrand.no>
Sent: Thursday, September 27, 2001 3:22 AM


> > Exceptions to MUST NOTs means there are cases which are not prohibited.
> > The semantics gives me the implication that the appripriate requirement
> > level is placed between "SHOULD NOT" and "MAY".
> 
> MUST NOT means that you never do it, and any implementation that does it is 
> nonconformant to the spec.
> If you find that you have to do it in some case, you have found a bug in 
> the spec.

Somecases. However, ICMPv6 example case, described in the first mail of this thread, has not been found but already described in the spec; which is not a bug at all.

Jiwoong


> Note that English is a slippery language, and constructs like "MUST NOT do 
> X unless Y, Z and W occurs" and its semantic equivalents are quite common.
> 
> Most specs have bugs.
> 
>                      Harald