Re: [netmod] datastore-specific constraints

Randy Presuhn <randy_presuhn@alumni.stanford.edu> Fri, 14 December 2018 02:13 UTC

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From: Randy Presuhn <randy_presuhn@alumni.stanford.edu>
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Date: Thu, 13 Dec 2018 18:13:42 -0800
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Subject: Re: [netmod] datastore-specific constraints
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Hi -

On 12/13/2018 3:58 AM, Ladislav Lhotka wrote:
....
>>>>      <operational> SHOULD conform to any constraints specified in the data
>>>>      model, but given the principal aim of returning "in use" values, it
>>>>      is possible that constraints MAY be violated [...]
>>> According to the definition of SHOULD and MAY in RFC 2119, this sentence
>>> contradicts itself.
>>
>> I don't actually see the contradiction here.
>>
>> - SHOULD can be violated if there are good reasons to do so (otherwise
>> it is a MUST)
>> - The MAY, and its associated condition, explains some conditions under
>> which it is reasonable for the SHOULD to be violated.
> 
> MAY means "truly optional" (e.g. "because the vendor feels that it enhances the
> product"). Combining different RFC2119 terms is generally problematic.

 From the perspective of the receiver, there is no difference.
"Good reasons" tend to be subjective and there's generally no
way for the receiver to know whether those conditions are true
for the sender or its implementer.

Consequently, for the code processing a protocol stream, a "SHOULD"
describing that stream is equivalent to a "MAY", since it only
says that the behaviour described is *possible*, and, that under
conditions to which the receiver will not be privy, other things
may happen.

Randy