Re: [Rtg-yang-coord] naive question ??

[Qin Wu <[e-mail]>]

> 
> I think that the problem with MIB Modules was and is a lack of 
> knowledge of management in general and of SNMP in particular, within 
> any working group (e.g. IDR) and that is likely to be true with YANG 
> but at least a WG should be familiar with the technology and have a 
> sense of which elements to include in a data or information model, 
> even if the WG lacks the skills to turn it into YANG.
> 
> SNMP does have conformance which made it possible to create the one 
> MIB Module with basic, intermediate and advanced subsets.  YANG lacks 
> that but has if-feature which I see as complicated, easy to get wrong 
> both in terms of getting the statement correct with respect to the 
> logic that has been agreed, and in choosing when to use it or not.  (A 
> bit like novice programmers who learn that when two or three 
> statements appear more than once, they can be replaced by a procedure 
> or function, making the code shorter and harder to understand and 
> maintain).  I suspect that if-feature is much over-used and that the 
> cost of that will become apparent in a few years time.

One of YANG strong sides is the extensibility and augmentation. If-feature is very useful, but it should be carefully used. A much better way to design YANG models is using following

base model
standard extension model
proprietary extension model

With base model, a basic set of features is described. That model can be then imported into another model, like standard or proprietary extension model, and augmented with more features. This provides easier to read and maintenance of the code. Take a look at draft-ietf-netmod-acl-model for example.

Dean

[Qin]: Good point.