Re: [YANG] 7.8.3 unique statement

Andy Bierman <ietf@andybierman.com> wrote:
> Martin Bjorklund wrote:
> > So, the set of existing leafs must be unique within all list entries
> > (if the set is non-empty).
> > 
> 
> Whether a leaf is mandatory or optional is separate from the unique statement.
> 
> So the fully specified tuple must be present, and be unique [a b c]
> If optional 'b' is missing [a c] then the agent ignores that entry
> when enforcing the uniqueness property. (?!?)

Yes.

> > We'll have to try to find the right wording.
> > 
> >>        - what if some missing leafs have defaults (ensuring they will not be unique)?
> > 
> > I think we should say that the leaf MUST NOT have a default.
> 
> 
> no, what if the leaf is from a 'uses' expansion?

I don't understand.

> It is also OK to apply the default once.

So you would allow one instance with the default, and the rest has to
have values set?

> > One more thing that we have talked about adding, is to allow 'unique'
> > in an augment.  For example:
> > 
> >    augment /interface {
> >       unique "ifName";
> >       leaf ifName { ... }
> >       ...
> >    }
> > 
> 
> I would rather not add this feature until the requirements for "augments"
> are better understood.

Ok.

> <tangent>
> One augments concern: what does it mean to declare conformance to a module?
> If module FOO-MIB includes X and Y, but the vendor also has module
> MY-FOO-MIB that adds a mandatory Z, does that vendor really conform to FOO-MIB?
> A manager that only knows about FOO-MIB and not MY-FOO-MIB will not work,
> so IMO the agent MUST NOT advertise that it supports FOO-MIB.
> </tangent>

But that won't work.  If I impplement FOO-MIB, how do I know that
there is some other module somewhere that augments it?  I think we
have to restrict the augment to not augment with any mandatory nodes.

This is be similar to the rules for versioning - you are not allowed
to add mandatory nodes in a new revision of the module.  And the
reason in both these cases is the same - to make sure that clients
that uses the old revision (or not using the module with the augment)
still work.

/martin

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