Re: [netmod] Query about augmenting module from submodule in YANG 1.0

[Robert Wilton <[e-mail]>]

Hi William,

The github issue is really only to track this point for further 
discussion and to the avoid losing the useful discussion on the alias.

I think that there is often useful discussion on the NETMOD alias that 
ends up at least with a partial resolution, but that never gets 
documented anywhere.  In a few cases these end up as errata, but often 
they either get deferred to a future version, or are treated as 
collective wisdom from the WG participants.  For the latter case, I'm 
hoping that we can store the summary of some of these discussions on a 
community maintained wiki.


YANG 1/1.1 modules using sub-modules could be upgraded into a single 
YANG 2.0 module.  This is an allowed backwards compatible change with no 
changes to the node paths or namespaces.

The pertinent text is in RFC 7950, sec 11:

    o  A module may be split into a set of submodules or a submodule may
       be removed, provided the definitions in the module do not change
       in any way other than those allowed here.

Thanks,
Rob


On 21/08/2017 14:44, Ivory, William wrote:
> Hi Rob,
>
> That would make it very hard to update existing 1.x YANG models to use new features in YANG 2.x if they used submodules.  Maybe that's something that no one would ever consider doing anyway, or maybe YANG 1.1 already has similar differences to 1.0?  I had (perhaps naively) assumed that you could migrate a namespace / model from YANG 1.0 to 2.0?
>
> Regards,
>
> William
>
> -----Original Message-----
> From: netmod [mailto:[e-mail]] On Behalf Of Robert Wilton
> Sent: 21 August 2017 11:24
> To: [e-mail]
> Subject: Re: [netmod] Query about augmenting module from submodule in YANG 1.0
>
>
>
> On 09/08/2017 16:13, Juergen Schoenwaelder wrote:
>> On Wed, Aug 09, 2017 at 05:01:09PM +0200, Ladislav Lhotka wrote:
>>> I remember that in early stages of YANG there was some irrational
>>> fear of introducing too many namespaces, and submodules may be a
>>> consequence of it. As you write, submodules provide no benefits
>>> whatsoever in terms of modularity, but the overhead in terms of
>>> metadata, IANA registration etc. is pretty much the same as for
>>> modules.
>> In case YANG 2.0 is ever done, I suggest someone files a proposal to
>> remove submodules if the cost/benefit ratio is at odds. There is
>> nothing wrong with removing stuff that has been found problematic.
> I agree.
>
> I've added https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_netmod-2Dwg_yang-2Dnext_issues_26&d=DwICAg&c=LFYZ-o9_HUMeMTSQicvjIg&r=p8kyeK3u4ZYiaQ2ZPGqwkyXmQgBH6r5jpYiYWzhqJ48&m=l7c4IPL049A2bVVO14fyBMly211xU61xSHgPlAT7owI&s=-kR4fUtXArQy0RwWb32DpT1bP4X_cNqt2zJVoC0JiX8&e=
>
> Rob
>
>> The motivation for submodules was that organizations maintaining large
>> modules with multiple people can do so without having to mess around
>> with tools like m4 scripts to produce a single module from 'snippets'
>> and to avoid integration surprises. But perhaps using m4 scripts and
>> decent version control systems (that can integrate and compile on
>> checkin) is indeed cheaper than having submodules part of the YANG
>> language itself.
>>
>> /js
>>
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