Subject: Re: [netmod] why does deviation-stmt have restrictions?

From: Balazs Lengyel <[email-masked]>
Date: Mon, 05 Jan 2009 12:21:38 +0100

+1.

IMO the only restriction on deviations should be that: once you applied all deviations, the
resulting YANG model must be valid. (Which is nowhere stated today.)

Deviations are for documenting how people do non-standard (or stupid things). The assumption
that we can restrict what kind of strange things they will do is rather shaky. Today deviations
do not allow adding new nodes. So if someone does add a new node, we do not want that documented?
Balazs

Andy Bierman wrote:
> Hi,
> 
> It seems odd that we are placing lots of restrictions on
> what a deviation is allowed to change.  I even suggested
> that the builtin type MUST NOT change.
> 
> I think we have the completely wrong perception
> of deviation-stmt.  All these restrictions make
> is seem like deviations are an acceptable part of
> the data model.  You don't like a clause? -- then just
> replace it or remove it with a deviation-stmt.
> It's OK in YANG.
> 
> There is a strong chance your competitor in the market
> will not spin your deviations the same way.  Deviations
> are mostly documenting the manner in which the agent does the
> WRONG, INCORRECT, NOT COMPLIANT, NON-STANDARD thing.
> 
> In that respect, any valid YANG construct should
> be OK for a deviation (e.g., you cannot add a units-clause
> to a container, but you should replace the units
> clause on a leaf if you implemented the units wrong).

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