Hi Lou,

I think that this solution is inferior to the model presented in pre-09.

I would prefer that we publish pre09 instead, potentially including the -08 model in the appendix if that helps progress the document in a more expedient fashion.

Thanks,
Rob


On 22/02/2018 16:18, Lou Berger wrote:
Hi,

(I have a bunch of different roles WRT this work.  This mail is being sent as an individual - as chair, I fully support the previous chair statements on this draft.)

Chris and I have come up with a proposal on how to provide full NMDA as part the existing schema-mount module.  Our motivation was to enable full NMDA support with *minimal* change to the model and disruption to the LC'ed work.  The key NMDA limitation, with -08, that we are aiming to address is the ability to support different mounted schema in different datastores for non-inline mount points. (See more detailed description below if interested full nuances of limitations of -08)

What we came up with was  to simply add a (leaf)list to identify in which datastores a schema-mount schema is valid/present. This is somewhat similar to YL-bis schema/module-set. Specifically we're proposing (see below for full tree below):

           +--ro schema* [name]
              +--ro name           string
ADD          +--ro datastore*    ds:datastore-ref {revised-datastores}

This approach has the advantages of supporting different mounted schema in different DSes, working with both NMDA and non-NMDA implementations, supporting all of the extensively discussed features of schema mount (including recursive mounts), and having minor/scoped impact on all dependent work.  The main downside is that it isn't the most optimal/compact solution possible if we were to base this work on YL-bis/pre09 draft.  Of course -08 isn't necessarily optimal from all perspectives, but it is what was agreed to as sufficient by those who contribute to the WG discussion.

In short, we see this as a solution to  addresses the raised last call issue with the minimal impact on -08 and dependent work -- which is what is appropriate given where we are in the process.

So our/my question really is:

    Is this a solution that you/all can live with?

Note: optimization, design preference and perfect alignment with use or YL-bis are not part of our question as we both don't think that is the right question given where we are in the WG process.

Lou (with ideas developed with Chris, and chair hat off)

======
Details -- for those who want
======
As background, my understanding/view is that the -08 version of the both NMDA and non-NMDA supporting implementations, but there are limitations in its NMDA applicability. Used with Yang Library, [rfc7895], only non-NMDA implementations can be supported.  When used with the revised Yang Library defined in [I.D.ietf-netconf-rfc7895bis-],  NMDA implementations  can be supported with certain limitations. Specifically, this document requires use of the now deprecated module-list grouping, and the same schema represented in schema list of the Schema Mount module MUST be used in all datastores.  Inline type mount points, which don't use the schema list,  can support different schema in different data stores not by instantiating the [I.D.ietf-netconf-rfc7895bis-] version of YANG library under the inline mount point.

    module: ietf-yang-schema-mount
        +--ro schema-mounts
           +--ro namespace* [prefix]
           |  +--ro prefix    yang:yang-identifier
           |  +--ro uri?      inet:uri
           +--ro mount-point* [module name]
           |  +--ro module        yang:yang-identifier
           |  +--ro name          yang:yang-identifier
           |  +--ro config?       boolean
           |  +--ro (schema-ref)?
           |     +--:(inline)
           |     |  +--ro inline?       empty
           |     +--:(use-schema)
           |        +--ro use-schema* [name]
           |           +--ro name
           |           |       -> /schema-mounts/schema/name
           |           +--ro parent-reference*   yang:xpath1.0
           +--ro schema* [name]
              +--ro name           string
ADD          +--ro datastore*    ds:datastore-ref {revised-datastores}
              +--ro module* [name revision]
              |  +--ro name                yang:yang-identifier
              |  +--ro revision            union
              |  +--ro schema?             inet:uri
              |  +--ro namespace           inet:uri
              |  +--ro feature*            yang:yang-identifier
              |  +--ro deviation* [name revision]
              |  |  +--ro name        yang:yang-identifier
              |  |  +--ro revision    union
              |  +--ro conformance-type    enumeration
              |  +--ro submodule* [name revision]
              |     +--ro name        yang:yang-identifier
              |     +--ro revision    union
              |     +--ro schema?     inet:uri
              +--ro mount-point* [module name]
                 +--ro module        yang:yang-identifier
                 +--ro name          yang:yang-identifier
                 +--ro config?       boolean
                 +--ro (schema-ref)?
                    +--:(inline)
                    |  +--ro inline?       empty
                    +--:(use-schema)
                       +--ro use-schema* [name]
                          +--ro name
                          |       -> /schema-mounts/schema/name
                          +--ro parent-reference*   yang:xpath1.0

We would expect that the revised-datastores feature would be used
(perhaps required) for any implementation that supports ietf-datastores
and yl-bis.



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