Re: [yang-doctors] guideline for enum and value?

[Juergen Schoenwaelder <[e-mail]>]

On Thu, Jan 25, 2018 at 09:18:27AM +0100, Benoit Claise wrote:
> Dear all,
> 
> Still busy with the RFC6087bis AD review, reviewing the enum sections now.
> 
> Do I recall correctly a guideline about not using "value" in enum?
> Something to be inserted in RFC6087bis? At least a pros and cons discussion?
>

I would rather say the opposite:

  YANG automatically assigns numeric values to enums if no values are
  specified. This automatic assignment requires that (a) the order of
  enums never changes and (b) additional enums are only appended but
  never prepended or inserted. This is subtle and using explicit value
  assignments, though more verbose, tends to be more robust when
  modules are revised.

Background:

Note that NETCONF and RESTCONF do not send the numeric values due to
the way the XML and JSON encodings are defined. But this may be
different for other encodings, the proposed CBOR encoding uses the
numeric value. Some implementations do support mappings to protocols
such as SNMP where numeric values are used.

We had a longer discussion about this when we talked about how we deal
with timezones, which change regularly and have no natural numeric
value. Algorithms to produce YANG enumerations from the timezone
databases are difficult if you want to have stable numeric values.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <https://www.jacobs-university.de/>