Re: [netmod] Augmenting an unimplemented module

Christian Hopps <chopps@chopps.org> writes:

> Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> writes:
>
>> On Fri, Feb 03, 2017 at 08:40:06AM -0500, Christian Hopps wrote:
>>>
>>> Is it allowed for a server to implement a module that augments another
>>> module that it does not implement? My thinking was that the augment
>>> would simply not be implemented in this case. Is that true or must the
>>> server implement any and all augmented modules referenced by a module?
>>>
>>
>> There are modules that only consists of augmentations. It would be
>> really odd if an implementation claims to have implemented such a
>> module without implementing the module that has been augmented.  For
>> example, it would be odd to claim an implementation of ietf-ip without
>> implementing ietf-interfaces.
>>
>> I think the proper thing to do is to write explicit deviations if a
>> portion of a module is not implemented (regardless whether the portion
>> is an augmentation or not).
>
> Well sure it's odd for an augmenting only module. In my case I'm adding
> a feature to another module that is not required for my module to be
> useful. My module is quite simple, conversely the module it augments
> (yang library) isn't. I didn't want to force the implementer to have to
> implement yang library, but I do want to add to it if they do.
>
> In any case is there anything explicit in the standard to indicate that
> a deviation must be indicated if an augmented module is not present?

RFC 7950 says in sec. 5.6.5:

   If a server implements a module A that imports a module B, and A uses
   any node from B in an "augment" or "path" statement that the server
   supports, then the server MUST implement a revision of module B that
   has these nodes defined.  This is regardless of whether module B is
   imported by revision or not.

Lada

> Might be nice to have an ability to tag the augmentation as optional.
>
> Thanks,
> Chris.
>
>>
>> /js
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