[netmod] Defining groupings after the fact? draft-jouqui-netmod-yang-full-include and the reuse of definitions

[Alexander L Clemm <[e-mail]>]

Hello Jean, Benoit, Thomas,

After your presentation at IETF 120, I looked at your draft
https://datatracker.ietf.org/doc/html/draft-jouqui-netmod-yang-full-include-02.


I do have some questions regarding what happens if the embedded module
is being augmented.  Is the augmentation automatically embedded as well;
does such embedding need to be explicitly stated?  Is there a way to
augment an embedded module only within the context of the embedding module?

On a more general note, it strikes me that there is an increased need in
reusing definitions.  In various forms, we see this in your use cases,
in network inventory use cases, in schema-mount, in peer-mount.  YANG
does not provide good support for that, which is somewhat ironic in that
it does actually support several constructs with reuse and extensibility
in mind, from identities to groupings.  Hopefully the YANG-next effort
will go a long ways towards improving definition reuse to that the need
for after-the-fact bandaids can be avoided.

When it comes to reusing parts of definitions, it seems that a lot of
grief could be avoided if portions that are to be reused would have been
defined as groupings, which could then be used wherever needed.  The
problem is that the grouping construct is rarely used, so many YANG
definitions are not available for reuse that otherwise might be.

As a thought, it might be useful to introduce a construct that will
allow to define a _grouping_ after-the-fact, for later reuse.  I.e.,
allow groupings to be defined in a way that the new grouping embeds an
existing definition, then simply make use of that grouping.  That would
seem perhaps cleanest, able to address many of the use cases and have
the additional advantage that the semantics here will be very clear
since part of the exising YANG framework.

--- Alex