Re: [YANG] default values

[Ladislav Lhotka <[e-mail]>]

Hi Balasz,

in my view, the basic difference is this:

Do we want to use (YANG or other) data models
(i) for validating XML documents in the NETCONF context, or
(ii) for specifying behaviour of network devices and/or management
software?

I am primarily interested in creating standard data models for (i) and
concerned that pursuing (ii) might make the result unusable for (i).
Note that the default statement makes sense only in (ii).

Lada


Balazs Lengyel píše v Čt 17. 01. 2008 v 09:54 +0100:
> Hello,
> I think you are arguing about different things. As I understand your comments:
> Statement 1) says: defaults are important, so if we do have an agreed default value, we should 
> document it in a proper, formal way. (I fully support this.)
> Statement 2) says: it is very difficult to agree on good default values so we should use 
> extreme caution specifying "mandatory" defaults in standards. I can agree with that as well.
> We can still to define recommended-only defaults in the description statement if the default is 
> not obvious enough.
> 
> The two statements do not contradict each other in my view.
> 
> Also while it is difficult to define default values in standards, YANG and NETCONF will be used 
> a lot to define proprietary data models as well. It is much easier to define defaults here, and 
> yes we do want a formal definition of these defaults (actually we already have it in the 
> Ericsson-DML.)
> 
> Balazs
> 
> 
> Ladislav Lhotka wrote:
> > Jon Saperia píše v St 16. 01. 2008 v 11:54 -0500:
> > 
> >> I understand your perspective but even  though I said what I said, if  
> >> we were to go down this path, defaults can be helpful.  Any manager  
> >> that attempts the configuration function will have to be pretty  
> >> sophisticated because of the variability (even with standards) that  
> >> will be sure to exist. That does not mean that they will not do bad  
> >> things from time to time, but the market has a way of fixing things.
> > 
> > I am not against specifying defaults (reasonably), I only don't like the
> > fact that changing a default value implies a different data model. I
> > understand the data model primarily as a means for checking whether a
> > given document is valid or not and default values are irrelevant in this
> > respect. It is already difficult to standardise the knobs and default
> > values are yet another level.
> > 
> > Lada
> > 
> >> /jon
> 
-- 
Ladislav Lhotka, CESNET
PGP Key ID: E74E8C0C



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