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

["Jason Sterne (Nokia)" <[e-mail]>]

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