Re: [netmod] yang-data-ext issues

Kent Watsen <> Tue, 01 May 2018 20:34 UTC

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From: Kent Watsen <>
To: Juergen Schoenwaelder <>
CC: NetMod WG <>
Thread-Topic: [netmod] yang-data-ext issues
Date: Tue, 1 May 2018 20:33:58 +0000
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Subject: Re: [netmod] yang-data-ext issues
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Juergen writes:
> Kent writes:
>> I don't understand talk about abandoning this draft.  There is no question
>> that it is needed (e.g., anima vouch, zerotouch, tail-f's "structure"),
>> and RFC 8040 is unsatisfactory because 1) it doesn't allow a top-level
>> 'choice' between two containers and 2) it requires drafts to reference 
>> RFC 8040, even though the drafts may have nothing to do with RESTCONF.
> Re 1: RFC 8040 says: "It MUST contain data definition statements that
> result in exactly one container data node definition." So a choice may
> actually work as long as the result is exactly one container data
> node. OK, the wording in the RFC 8040 statement is not clear since
> 'result' and 'definition' do not line up (does 'result' mean the
> toplevel data node instances that are possible? In this case,
> 'definition' would be misleading).

I agree, but Martin did not and he even modified `pyang` to throw an 
error on the zerotouch draft, thus forcing the current situation.  If
a new understanding regarding rc:yang-data can be reached, the zerotouch
draft can go back to using it.

> Re 2: It does not really matter whether you import the extension from
> RFC 8040 or some other module. Why is depending on A better than
> depending on B? The definition in RFC 8040 is already know by tools.
> I view the yang-data definition of RFC 8040 as a temporary solution, a
> proper solution should in my view be part of YANG 1.x.

What is the "proper solution", and why does it need to wait for YANG 1.x?
In the discussion regarding moving faster, it's been suggested that YANG 
1.x could be a cherry-picking of some number of extension statements 
produced in other I-Ds.  I was hoping that this was the case here.  True,
some tools know about A, but if B is the LTS, then I'd hope to move to B

> Since NMDA essentially binds all data tree definitions to datastores,
> the yang-data construct allows us to define data structures that are
> specifically not bound to any datastore, i.e., data structures that by
> design can't be operated on directly with NMDA NETCONF/RESTCONF.


Kent // contributor