Subject: [netmod] YANG semver: clarify reasoning for _COMPAT suffix

From: "Sterne, Jason (Nokia - CA/Ottawa)" <[email-masked]>
Date: Wed, 17 Nov 2021 19:29:46 +0000

Hi all,

https://datatracker.ietf.org/doc/html/draft-ietf-netmod-yang-semver-05#section-3.3 shows how the COMPAT suffix (_compatible or _non_compatible) is "sticky" but we could use some clarifying text to explain *why* that is useful.  This was raised in https://github.com/netmod-wg/yang-ver-dt/issues/84.

Here are some proposed edits in this PR:
https://github.com/netmod-wg/yang-ver-dt/pull/119

It is mainly adding this paragraph:

   The _COMPAT modifier string is "sticky".  Once a revision of a module
   has a modifier in the revision label, then all descendants of that
   revision will also have a modifier.  The modifier can change from
   _compatible to _non_compatible in a descendant revision, but the
   modifier would never change from _non_compatible to _compatible or be
   removed.  The persistency of the _non_compatible modifier ensures
   that comparisions of revision labels doesn't give the false
   impression of compatibility between two potentially non-compatible
   revisions.  If _non_compatible was removed, for example between
   revisions 3.3.2_non_compatible and 3.3.3 (where 3.3.3 was simply an
   editorial change), then comparing revision labels of 3.3.3 back to an
   ancestor 3.0.0 would look like they are backwards compatible when
   they are not (since 3.3.2_non_compatible was in the chain of
   ancestors and introduced an NBC change).

As well as the info in () here:

       iii  "X.Y.Z_non_compatible" - the artifact version SHOULD be
            updated to "X.Y.Z+1_non_compatible" (to ensure that
            information about a break in compatibility is not lost).

Jason

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From: "Joe Clarke (jclarke)" <[email-masked]>
Date: Wed, 17 Nov 2021 19:49:03 +0000

I left some comments in the GH pull request, Jason.  Mostly editorial, but I think there might be a need for a stronger bit of normative language in there as well.

Joe

On 11/17/21 14:30, Sterne, Jason (Nokia - CA/Ottawa) wrote:
Hi all,

Jason