Re: [netmod] yang-data-ext issues

Martin Bjorklund <mbj@tail-f.com> Wed, 02 May 2018 07:30 UTC

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Date: Wed, 02 May 2018 09:30:16 +0200 (CEST)
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To: kwatsen@juniper.net
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] yang-data-ext issues
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Kent Watsen <kwatsen@juniper.net>; wrote:
> 
> 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

Originally pyang did not check this, but I was convinced by Andy and
the discussion on the ML that pyang was not correct.

The intention of the text in RFC 8040 was to allow for "uses" within a
yang-data statement.  It was not to allow for "choice".

>, 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.

+1


/martin


> True,
> some tools know about A, but if B is the LTS, then I'd hope to move to B
> ASAP.
> 
> > 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.
> 
> Yes.
> 
> 
> Kent // contributor
> 
> 
> 
> 
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