Re: [netmod] Updated Content of Module Versioning - T8 (recommended-min for imports)

[Jürgen Schönwälder <[e-mail]>]

See draft-schoenw-netmod-yang-relaxed-versioning-00.txt.

A proper solution without bumping the YANG version number is
impossible. If the YANG version number can't be touched, then all you
can do is to document the NBC changes - and wait for a YANG next
project to fix the rest.

/js

On Wed, Oct 25, 2023 at 06:51:12PM +0000, Jason Sterne (Nokia) wrote:
> Can you clarify what you'd recommend then if we don't have it?
> 
> For example:
> -  IETF module A needs to import ietf-yang-types to use hex-string (only added in the 2013-07-15 version)
> 
> Use import but without a revision substatement?  (i.e. avoid import by specific revision)?
> 
> Add something to the description of module A to mention it needs at least 2013-07-15?
> 
> Jason
> 
> > -----Original Message-----
> > From: Jürgen Schönwälder <[e-mail]>
> > Sent: Wednesday, October 25, 2023 2:45 PM
> > To: Jason Sterne (Nokia) <[e-mail]>
> > Cc: [e-mail]
> > Subject: Re: [netmod] Updated Content of Module Versioning - T8
> > (recommended-min for imports)
> > 
> > 
> > CAUTION: This is an external email. Please be very careful when clicking
> > links or opening attachments. See the URL nok.it/ext for additional
> > information.
> > 
> > 
> > 
> > I am strongly against this. The import statement is used by tools.
> > Adding a recommendation for humans that existing and conforming tools
> > will not understand just causes confusion.
> > 
> > /js
> > 
> > On Wed, Oct 25, 2023 at 06:41:19PM +0000, Jason Sterne (Nokia) wrote:
> > > Hi all,
> > >
> > > Starting a dedicated thread for T8 recommended-min for imports
> > >
> > > These are my own personal opinions (not those of the
> > authors/contributors).
> > >
> > > It has been discussed before that import by a specific revision is
> > somewhat broken (not recommended). It is mentioned in section 2.5 of the
> > versioning requirements draft: https://www.ietf.org/archive/id/draft-ietf-
> > netmod-yang-versioning-reqs-08.html#name-no-good-way-to-specify-whic
> > >
> > > Based on previous WG LC discussions, we already changed from a
> > revision-or-derived extension (that did affect conformance & what a tool
> > could/should use), to a weaker recommended-min in order to avoid further
> > changes to the YANG language & conformance rules.  The recommended-
> > min is pretty much purely a documentation tag that helps users of the
> > modules understand what versions of imports might be best to use (e.g.
> > when supporting multiple modules in a server, or constructing a "package"
> > of modules that work together).
> > >
> > > We could instead just say to put this information into a description field in
> > the module. But it is helpful if the field is broken out (i.e. structured data)
> > and more easily machine readable.
> > >
> > > So I'd like to see this stay as part of Module Versioning but be renamed to
> > recommended-min-date.  Then in YANG Semver we should add
> > recommended-min-semver-label.
> > >
> > > Jason
> > >
> > >
> > > From: netmod <[e-mail]> On Behalf Of Jason Sterne
> > (Nokia)
> > > Sent: Tuesday, October 24, 2023 9:58 AM
> > > To: [e-mail]
> > > Subject: [netmod] Updated Content of Module Versioning
> > >
> > > Hello NETMOD WG,
> > >
> > > The YANG versioning authors and weekly call group members have been
> > discussing the next steps for the versioning drafts.
> > >
> > > We'd propose that the first step is to converge on what aspects of the
> > current Module Versioning draft should be retained, and which parts should
> > be removed. We can then work towards a final call on an updated version
> > with this revised scope.
> > >
> > > Below is a summary of the main topics in the Module Versioning draft.
> > We've divided the items T1-T10 into 2 groups:
> > > A) Baseline content of Module Versioning
> > > B) Items which need more WG discussion
> > >
> > > In addition to whatever discussions happen on this email list, we have also
> > created a hedgedoc where you can register your preference for items T7-
> > T10. It would be much appreciated if you can put your opinion in the
> > hedgedoc here:
> > > https://notes.ietf.org/CdKrT5kVSF6qbnRSY4KeSA?both
> > >
> > >
> > > GROUP A (Baseline content of Module Vesioning)
> > > -----------------------------------------------------------------
> > > Based on resolution of WG LC comments and subsequent discussions, and
> > some feedback to reduce complexity and content in the Module Versioning
> > draft, here is a summary of items that will and won't be part of the next
> > update of the Module Versioning draft (also referred to as "this draft"
> > below).
> > >
> > > T1. The "ver:non-backwards-compatible" annotation (Sec 3.2):
> > > Retained. This top level (module level) extension (which can be ignored by
> > tools that don't understand it) is critical to include so that module readers
> > and tools can know when NBC changes have occurred.
> > >
> > > T2. Updated rules of what is NBC: (Sect 3.1.1, 3.1.2)
> > > Retained. These are updates/clarifications (i.e., changes) to the RFC 7950
> > rules that are appropriate and helpful:
> > > (i) "status obsolete"
> > >   - This draft changes RFC 7950 so that marking a data node as obsolete is
> > an NBC change because it can break clients.
> > > (ii) "extensions"
> > >   - This draft changes the RFC 7950 rules to allow extensions to define the
> > backwards compatibility considerations for the extension itself.  The existing
> > RFC 7950 rules only allow extensions to be added, not changed or removed.
> > > (iii) "import by revision-date"
> > >   - This draft changes the RFC 7950 rules to allow the revision date of an
> > import-statement to be changed/added/removed.  The imported module
> > must be versioned separately (i.e., by a YANG package/library defining the
> > schema).
> > > (iv)  "whitespace":
> > >   - This draft clarifies the existing RFC 7950 behaviour that changing
> > insignificant whitespace is classified as a backwards compatible change
> > >
> > > T3. revision-label-scheme extension (Sec 3.4.2)
> > > Removed. Based on WG LC discussions we will go back to a single
> > versioning scheme for YANG modules, and hence the revision-label-scheme
> > extension will be removed from this draft.
> > >
> > > T4. revision-label extension (Sec 3.4)
> > > Removed. Related to T3 above, given that a single versioning scheme is
> > sufficient, the revision-label extension will be moved to the YANG Semver
> > draft, and removed from Module Versioning.
> > >
> > > T5. Resolving ambiguous imports in YANG library (Sec 5.1)
> > > Removed. This will be removed from Module Versioning (could be
> > considered in YANG Next, although that is many years away).  Note, RFC
> > 7950, section 5.6.5, paragraph 5 does consistently define how to build the
> > schema.  The change in the draft was to always prioritise an implemented
> > module over the most recent implemented *or* import-only revision. But
> > this will be removed.
> > >
> > > T6. Advertisement for how deprecated & obsolete nodes are handled (Sec
> > 5.2.2)
> > > Retained. This information is important for clients to be able to accurately
> > construct the schema and hence it is retained in Module Versioning.
> > >
> > > GROUP B (Needs WG discussion)
> > > -------------------------------------------
> > > For these items we don't have consensus within the WG - they need more
> > discussion and input.
> > >
> > > It is recommended to go back and look at the NETMOD emails on these
> > topics (from the WG LC discussions).
> > >
> > > Please add your name beside your preferred option in the poll:
> > https://notes.ietf.org/CdKrT5kVSF6qbnRSY4KeSA?both
> > >
> > > T7. filename changes (Sec 3.4.1)
> > > The authors/contributors are leaning towards suggesting that this moved
> > change be moved to YANG Next consideration.  However, there isn't
> > complete consensus, with concerns that the vendors will each define their
> > own incompatible file naming schemes for YANG modules that use version
> > numbers.  If we retain this work then this would likely move to the YANG
> > Semver draft.
> > > [See hedgedoc poll T7]
> > >
> > > T8. recommended-min for imports (Sec 4)
> > > The WG seems to be somewhat split on how urgent this is, and there isn't
> > consensus amongst authors/contributors for retaining this work or
> > deferring it. One option is to keep it, but renamed as recommended-min-
> > date.
> > > [See hedgedoc poll T8]
> > >
> > > T9. Versioning of YANG instance data (Sec 6)
> > > There wasn't any consensus among the authors/contributors as to
> > whether this should be retained or deferred to a new version of the YANG
> > instance data document.
> > > [See hedgedoc poll T9]
> > >
> > > T10. Do *all* whitespace changes (including whitespace between
> > statements) require a new revision to be published? Sec 3.1, last paragraph.
> > > The authors/contributors are somewhat split on whether to retain this.
> > The advantage of keeping this is that it makes it very easy to check (i.e., via a
> > simple text diff tool) whether two modules pertaining to be the same
> > version are in fact the same.  It should also mean that it is easy to generate
> > a hash-based fingerprint of a module revision.  The alternative gives more
> > flexibility to users to reformat modules (e.g., for different line-lengths), but
> > complicates the check to ensure that a YANG module revision hasn't been
> > changed or makes it slightly more expensive to generate a hash since the
> > module formatting would need to be normalized first.
> > > [See hedgedoc poll T10]
> > >
> > > Jason (he/him)
> > >
> > 
> > > _______________________________________________
> > > netmod mailing list
> > > [e-mail]
> > > https://www.ietf.org/mailman/listinfo/netmod
> > 
> > 
> > --
> > Jürgen Schönwälder              Constructor University Bremen gGmbH
> > Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
> > Fax:   [phone]         <https://constructor.university/>

-- 
Jürgen Schönwälder              Constructor University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <https://constructor.university/>