Subject: [netmod] conformance discussion status

From: Juergen Schoenwaelder <[email-masked]>
Date: Tue, 3 Mar 2015 11:09:31 +0100

Conformance high-level summary after the 2015-02-18 call:

It seems that typedef and grouping drift and the most pressing
problems to be solved.

a) It appears that neither import-by-revision nor
   import-by-min-revision can be made to work to solve the typedef and
   grouping drift problems.

b) One option is to simply disallow typedef drift and grouping drift,
   i.e., any such change requires to define a new typedef or grouping.

c) One could relax option b) by allowing typedef and grouping drift
   (e.g., for vendors that have a versioning / release model that
   handles ambiguity issues) in the base specification but requiring
   that IETF modules are not allowed to have typedef and grouping
   drift.

d) Another option is to have explicit conformance statements that are
   maintained separate from the data definitions and these conformance
   statements are kept stable (drift free) while other definitions may
   drift.

Another related drift issue is multiple augments of something that
exists in multiple versions.

Some other things observed:

1) The definition of 'deprecated' and 'obsolete' may need some
   clarification.

2) The uses statement perhaps lacks a mechanism that can be used to
   restrict the components of a grouping that are used.

3) It also seems that uses statements are difficult to expand mentally
   and that descriptions in groupings are either general and thus very
   unspecific or they kind of specific but then the grouping can be
   used where they do not really make sense, or are even wrong.

There is some general question how many client applications are taking
benefit from being able to precisely determine from the advertised
data models what the server supports, that is, what the practical
value of addressing all the axioms stated in Martin's draft are.
Perhaps a phased approach is possible where certain things (e.g., the
drift issues mentioned above) are addressed in YANG 1.1 while a
broader conformance solution may be done later once we have more
experience with data model revisions and we better how client tools
take advantage of the machine readable information available (i.e, how
data model driven client really are).

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>