Re: [netmod] handling module incompatibility

[Juergen Schoenwaelder <[e-mail]>]

On Fri, Oct 06, 2017 at 03:49:50PM +0100, Robert Wilton wrote:
> Hi,
> 
> On 06/10/2017 14:25, Lou Berger wrote:
> > Hi,
> > 
> >      As part of the my Routing Directorate review of
> > draft-wu-l3sm-rfc8049bis I noted that there were several incompatible
> > changes being made to the ietf-l3vpn-svc module without changing the
> > name.  I raised this with the YANG doctors and others involved with the
> > draft and it surfaced some topics which really should be discussed here
> > in NetMod.
> > 
> > The background (as explained off-list by others, so I hope I have it
> > right)  is that one of the YANG Doctors noted that RFC8049 was broken
> > and could not be implemented as defined, and therefore a fix was
> > needed.  L3SM has concluded so the fix is in the individual draft
> > draft-wu-l3sm-rfc8049bis.  Since the rfc8049 version of ietf-l3vpn-svc
> > module could not be implemented, the feeling by the YANG Dr was that
> > even though the new module is incompatible with the original definition
> > the module the rule defined in Section 11 of YANG 1.1 (or section 10 of
> > RFC 6020) didn't have to be followed and the same name could be used.
> 
> I think that this is the view that I support as well.  If something is
> clearly broken then it should be possible to fix it without requiring a new
> module name, just an updated revision.
>

The hidden question is what is 'broken' or 'clearly broken' and when
are definitions in a module broken and when is the damage so big that
the whole module is broken. Does a broken xpath statement cause the
whole module to be fundamentally flawed such that an implementation of
the rest is impossible?

It is not uncommon to find errors in data models and it is then often
a matter of a new revision or errata to address those. The question
here is when is an entire module broken up to the point that nobody
ever will have implemented it or parts of it.

I do not know the answer but I see a certain risk that minor bugs will
be used to argue none of the YANG update rules apply.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <http://www.jacobs-university.de/>