Re: [netmod] comments on draft-jouqui-netmod-yang-full-include

[Andy Bierman <[e-mail]>]

On Tue, Apr 16, 2024 at 7:01 AM Benoit Claise <[e-mail]>
wrote:

> Hi Andy,
>
>
> On 3/21/2024 5:35 PM, Andy Bierman wrote:
>
> Hi,
>
> The presentation yesterday helped me understand the motivation for this
> work.
> Seems simple enough, but rife with unintended consequences.
> RFC 8528 does a good job of dealing with most of these issues, but it is
> not a design-time
> modification like this draft is proposing.
>
> I would like to see this work as part of yang-next, but not thrown in with
> YANG 1.1.
>
> Yes, we could always push enhancement to YANG-Next.However, don't we have
> enough requests now, not only from the IETF (
> draft-ietf-opsawg-collected-data-manifest
> <https://datatracker.ietf.org/doc/draft-ietf-opsawg-collected-data-manifest/>)
> but also from the BBF (Scott Mansfield) and 3GPP (Balazs), as mentioned in meeting
> minutes
> <https://datatracker.ietf.org/doc/minutes-119-netmod-202403210300/>?
> Let's keep in mind that
> I don't see YANG-Next being standardized any time soon.
>
>

I don't see how this type of Schema Mount can be achieved without
specifying which
modules are included at the mount point.  It looks like a special "import"
mechanism will be needed
so a YANG 1.1 tool does not think a module is being used at the top-level.

IMO it is a bad idea to reinvent parts of the YANG language as external
language statements.

Regards, Benoit
>
>
>

Andy


> Just some of the major issues to solve:
>
> 1) XPath
> The issue of leafrefs was raised but of course this also applies to
> must/when statements.
>
> 2) Shared yanglib
> This draft shares the top yanglib.
> Schema Mount implementations allow completely separate YANG libraries
> that are decoupled from the top yanglib and other mount points.  This
> allows
> deviations, features, etc.
>
>
> 3) No way to include data nodes only at the mount point.
> To a YANG 1.1 tool, if a module is listed in the yanglib then all its
> implemented top-level objects are part of <running>.
>
> 4) Not clear what is included and scoped at the mount point
> There are lots of top-level YANG statements that are not data-def-stmts.
> Are these ignored? What exactly is included?  What changes to identifier
> scope resolution
> are being made?
>
> 5) anydata as root
> This causes more problems than it is supposed to solve.
> IMO Schema Mount got this right, keeping it a container or list.
>
> 6) Recursion and Loops
> This adds significant complexity to the implementation.
>
> IMO this is an interesting topic for yang-next.
>
> Andy
>
>
>
>
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