[netmod] Y34

[Ladislav Lhotka <[e-mail]>]

Hi,

after listening to the presentation of
draft-rtgyangdt-rtgwg-device-model-00 at RTGWG session, I am wondering
whether the solution chosen for Y34 is really useful.

The draft states they want to reuse ietf-interfaces but their tree in
fact is

   +--rw device
          +--rw info
          |  +--rw device-type?   enumeration
          +--rw hardware
          +--rw interfaces
          |  +--rw interface* [name]
          |     ...
          +--rw qos

So the "interfaces" container is no more a top-level node. There are
three possible options:

1. Change the ietf-interfaces module.
2. Replicate its contents in another module.
3. Extend YANG so that a *specific* schema tree can be grafted at a
   given data node.

IMO #1 & #2 are really bad. I thought Y34-04 was essentially #3 but it
seems it is not so because it doesn't specify a concrete data model
that's allowed at a given location.

On the other hand, the only real contribution of "anydata" over "anyxml"
is that is doesn't permit mixed content in XML, which is IMO not much.

I know Y34 was already closed but I think it is more important to do
things right before YANG 1.1 becomes an RFC.

What I want to propose is this:

- Rename "anydata" as a synonym to "anyxml", and deprecate "anyxml" (but
  keep it for backward compatibility).

- Introduce a new statement and data node type, e.g. "root", that will
  extend the schema tree starting from that data node with a precisely
  specified data model. The specification can be same or similar as
  in yang-library.

I believe there are other use cases in the existing modules. For
example, the ietf-routing module could simply define the data model for
a single routing instance (i.e. without "routing-instance" list at the
top), and it can be then used without changes on simple devices, and
more complex router implementations can graft it as a subtree under
"routing-instance", "networking-instance" or whatever.

Lada

-- 
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: E74E8C0C