[netconf] Which is the better way for vendor-specific extension?

[yuchaode <[e-mail]>]

Hi friends,

Since the definition of standard cannot always cover all the attributes of different vendors, vendor-specific extension is necessary to exist.
Especially for IETF YANG data model, some of our drafts takes years to release. Vendors cannot wait for all the drafts are released, and their development has to begin with an immature version, and make some extensions based on their owned understanding.

When I learned YANG language on my first time, people told me that we can use some vendor-specific YANG models to augment the existing models to make this vendor-specific extension.
For example, there is an ietf-example.yang, in which there are three attributes named attr-1, attr-2, attr-3.
Vendor A thinks that these three attributes are not enough, he would like to extend attr-4. He can write a vendor-a-ext.yang to specify this attribute.
So when to retrieve the ietf-example data, for vendor A, he can response with:
{
 "ietf-example:root": {
"attr-1": a,
"attr-2": b,
"attr-3": c,
"vendor-a-ext:attr-4": d
  }
}

In multi-vendor scenario, there could be a lot of vendor-specific extension. If the source structure is very complex, the vendor-specific extension could be everywhere, this is messy and will be a heavy burden for the orchestrator.
Is there any suggestion to deal with these flexible vendor-specific extension?

In some traditional protocols, such as CORBA, a fixed name-value pair structure is provided for vendor-specific extension.
For vendor A's scenario, it can work like below (here I use json format for better comparison):
{
  "root": {
"attr-1": a,
"attr-2": b,
"attr-3": c,
   "additional-info": {
"name": "vendor-a-ext:attr-4",
"value": d
}
}
}
So for the orchestrator, it is easy to recognize which part of attributes are standard and which part of attributes are vendor-specific. It will be of great help for their programing.

I remember there used to be a discussion and opposed to introduce this opaque structure, which was said to be harmful for standardization.
But I also found such kinds of experience in openconfig, such like the properties structure in openconfig-platform module.
So, which is a better way for vendor-specific extension?

The above is just my superficial views, welcome to have your comments. Thanks!

B.R.
Chaode