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Re: Question about BCP 14 / RFC 8174

Brian E Carpenter <brian.e.carpenter@gmail.com> Fri, 29 August 2025 20:47 UTC

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Date: Sat, 30 Aug 2025 08:47:44 +1200
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Subject: Re: Question about BCP 14 / RFC 8174
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Regards/Ngā mihi
    Brian Carpenter

On 30-Aug-25 06:33, Michael Richardson wrote:
> 
> Rob Wilton \(rwilton\) <rwilton=40cisco.com@dmarc.ietf.org> wrote:
>      > Picking up on Brian’s prose, arguably writing “MUST xxx UNLESS yyy”,
>      > “MUST NOT aaa UNLESS bbb” would be even clearer to readers.  A slightly
>      > out-there suggestion could be to update RFC 2119 to remove
>      > SHOULD/SHOULD NOT and introduce MUST … UNLESS and MUST NOT … UNLESS as
>      > their replacements.
> 
> I would support that.

I think that John Klensin correctly pointed out the historical baggage
that makes that change quite awkward. But maybe it would be good if, to
back up the IESG statement, we made sure at Last Call review time that
every SHOULD/RECOMMENDED carries an "unless" condition or equivalent.

    Brian

> 
>      > That would make specifications more precise and prevent folks from
>      > using SHOULD to sit on the fence.
> 
> I think that people use SHOULD because MUST feels too emphatic.
> It does not feel very polite.
> But, it's not an invitation (in Caligraphy) to your great aunt for tea, it's
> a technical specification.
> 
> --
> Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
>   -= IPv6 IoT consulting =-                      *I*LIKE*TRAINS*
> 
> 
>

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