[rfc-i] Drafting issue... use of MAY

Martin J. Dürst duerst at it.aoyama.ac.jp
Wed May 2 18:15:03 PDT 2018


On 2018/05/03 08:49, Barry Leiba wrote:
> What value does the "MAY" give you there?  Why might I close the
> session?  Why might I not?  How do I decide?  What, exactly, is it
> that you, the spec writer, are telling me to *do* by using "MAY"
> there?

Please go back and read Dave Thaler's post again (which I think gives 
the best explanation). If you're implementing the client, then this MAY 
tells you that you MUST be able to handle the server closing the 
session. Such constellations are quite frequent in specs, and that's why 
having MAY as a short way of saying so is helpful.

As for the server, what the spec says is only that this way of handling 
things is an option. It doesn't tell the server implementer why it might 
close the session, or why not. It doesn't tell the server implementer 
how to decide.

The reason for this is that the spec writer, and the WG, understood that 
the server implementer would be in a much better position to decide what 
to do. A server implementer could close the connection because it's a 
very simple implementation, and closing the connection is the simplest 
thing to do. It could close the connection because it tried other things 
with this specific client, without satisfactory results. It could close 
the connection because it wants to test that the client can handle that. 
And so on. When writing specs, we are assuming that the implementers 
that read them have good reasons to choose one or more of the 
possibilities that the spec offers.

Regards,   Martin.

> Barry
> 
> On Wed, May 2, 2018 at 5:37 PM, Carsten Bormann <cabo at tzi.org> wrote:
>> On May 2, 2018, at 21:25, Barry Leiba <barryleiba at computer.org> wrote:
>>>
>>> AS WRITTEN
>>>    When <this happens> the server MAY close the client session."
>>>
>>> BETTER
>>>    When <this happens>, the server is likely to close the client
>>>    session, and clients MUST be able to handle that situation.
>>
>> Not better.  Circumlocution does not help.  The MAY version here is exactly what you should write in this case.
>>
>> (Of course, for more specific values of “handle that situation”, the MUST version may be appropriate.
>> But unsubstantiated judgement calls such as “is likely to” don’t belong into the spec.)
>>
>> Grüße, Carsten
>>


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