Re: [mpls] [netmod] Use of schema mounts for common model

[Martin Bjorklund <[e-mail]>]

"Tarek Saad (tsaad)" <[e-mail]> wrote:
> Hi authors/WG,
> 
> In draft-ietf-teas-yang-te, we are driving the definition for a
> generic TE YANG model that can/may be used (and extended when
> necessary) for different data plane technologies (e.g. MPLS, OTN, WDM,
> etc.).
> Reviewing the schema mount idea presented in
> draft-ietf-netmod-schema-mount, we are thinking this proposal is
> useful and can facilitate the reuse of the our model in multiple
> places in the YANG tree (once per each technology), e.g.:
> …/mpls/mount-points/mount-point/module=ietf-te.yang
> …/otn/mount-points/mount-point/module=ietf-te.yang

Schema mount is probably not the right solution to your problem.  I
think a better solution in your case is to define groupings.
Groupings are designed to be re-used at different places in the
hierarchy.

> We have a comment/concern/suggestion and we value your feedback.
> 
> The generic TE model currently references data nodes in the global
> tree (e.g. from the ietf-interfaces model to define additional TE
> properties associated with a specific device interface). Our
> understanding after reading section 3.1 of your draft is the mounted
> model can *not* reference any data nodes outside the scope of the
> mount-point (e.g. global data nodes in the yang tree). This poses a
> limitation for us, do you have a suggestion for this problem?
> 
> One possible solution we thought of was to replace the leaf-refs
> pointing to the global data nodes (e.g. Ietf-interfaces) with context
> names (e.g. the interface name).. This decouples the data-nodes
> defined in the TE generic model from those in the global tree
> (e.g. the actual interface ietf-interfaces model). Any feedback on
> this or better suggestions?

If you use groupings instead, you can still use proper leafrefs.


/martin



> 
> Regards,
> Tarek
> 
> Excerpt from draft-ietf-netmod-schema-mount
> 
> 3.1<https://tools.ietf.org/html/draft-ietf-netmod-schema-mount-01#section-3.1>.
> Augment and Validation in Mounted Data
> 
> 
>    All paths (in leafrefs, instance-identifiers, XPath expressions, and
>    target nodes of augments) in the data models mounted at a mount point
>    are interpreted with the mount point as the root node, and the
>    mounted data nodes as its children.  This means that data within a
>    mounted subtree can never refer to data outside of this subtree.
> 
> 
> 
>