RE: New Version Notification for draft-leiba-rfc2119-update-00.txt

["Dearlove, Christopher (UK)" <[e-mail]>]

Plenty of standards use shall, but never must, as their imperative word. For example (the first standard I had to hand) ISO 27001 has many occurrences of shall (not capitalised, that seems to be an IETF special) and none of must.

Shall is hard in English (outside standards). For a start there’s the shall/will issue, see for example http://www.oxforddictionaries.com/words/shall-or-will

(And where it says “In practice”, that may or may not be so if you have an editor or a customer with strong views. Or hold such views yourself.)

But since standards are not written in the first person,  when shall and will are differentiated, from that link, shall is “a strong determination to do something”. Not quite that same as a standardese instruction (unless we view it as the strong determination of the instructor).

Which all is why RFC 2119 exists.

--
Christopher Dearlove
Senior Principal Engineer
BAE Systems Applied Intelligence Laboratories
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From: Ted Lemon [mailto:[e-mail]]
Sent: 11 August 2016 13:57
To: Stewart Bryant
Cc: Dearlove, Christopher (UK); Barry Leiba; IETF discussion list
Subject: Re: New Version Notification for draft-leiba-rfc2119-update-00.txt


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The problem with SHALL is that in other contexts it often means MUST, which is kind of weird, and not really what the english word means.   I tend to agree that it's worth advising against its use.

On Thu, Aug 11, 2016 at 7:44 AM, Stewart Bryant <[e-mail]<mailto:[e-mail]>> wrote:
Optional is useful in a requirements RFC.

Feature x is REQUIRED

Feature y is OPTIONAL

- Stewart



On 11/08/2016 12:27, Dearlove, Christopher (UK) wrote:
Grammatically, RECOMMENDED is sometimes useful, as using SHOULD instead can produce less clear sentences. In principal the same applies to OPTIONAL, but I've never had cause to use it.

I wouldn't miss SHALL. Except that SHALL is often the word used outside the IETF rather than must, and there may be many RFCs using it, so do need to keep the explanation, even if deprecated to use it in new documents.


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