Re: [netmod] Deviating away /interfaces-state

Hi,

Ladislav Lhotka <lhotka@nic.cz> wrote:
> On Mon, 2018-09-10 at 11:48 +0200, Balazs Lengyel wrote:
> > Hello,
> > We would like to remove the if:interfaces-state with a deviation as it will
> > never contain any information. So we wanted to use 
> > deviation /if:interfaces-state {
> >   deviate not-supported;
> > }

Yes, this is the proper way to do it.

> > 
> > However after this we get an error as ietf-interfaces has a definition:
> 
> I think this check really goes overboard.
>
> Sec. 9.9.2 in RFC 7950 says:
> 
>    The "path" expression evaluates to a node set consisting of zero,
>    one, or more nodes.  If the "require-instance" property is "true",
>    this node set MUST be non-empty.

It also says about the "path" statement:

   It takes as an
   argument a string that MUST refer to a leaf or leaf-list node.

The intention was that it is an error if the path doesn't refer to a
leaf[-list] schema node, but depending on "require-instance" the leaf
instance might not have to exist.

However, I do agree that it in this particular case, as long as the
type isn't used in the system, it should not be reported as an error.

/martin

> 
> However, evaluating an XPath expression make sense only in the context of a
> concrete instance data tree. Therefore, no error should be reported unless an
> instance of a leaf with the "instance-state-ref" type exists. With the typedef
> below, we are two steps away from that.
> 
> Lada  
> 
> >      /*
> >       * Legacy typedefs
> >       */
> > 
> >      typedef interface-state-ref {
> >        type leafref {
> >          path "/if:interfaces-state/if:interface/if:name";
> >        }
> >        status deprecated;
> >        description
> >          "This type is used by data models that need to reference
> >           the operationally present interfaces.";
> >      }
> > 
> > Here the path statement will point at a non-existent branch.
> > 
> > So is there a correct way to indicate we do not support /interface-state ?
> > regards Balazs 
> > _______________________________________________
> > netmod mailing list
> > netmod@ietf.org
> > https://www.ietf.org/mailman/listinfo/netmod
> -- 
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
> 
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