Re: [netmod] evaluation of "when" under NMDA

On Mon, Dec 4, 2017 at 9:05 AM, Ladislav Lhotka <lhotka@nic.cz> wrote:

> On Mon, 2017-12-04 at 17:34 +0100, Martin Bjorklund wrote:
> > Ladislav Lhotka <lhotka@nic.cz> wrote:
> > > Hi,
> > >
> > > if we have
> > >
> > > augment "/target/node" {
> > >   when "...";
> > >   ...
> > > }
> > >
> > > is the "when" expression supposed to be evaluated separately in each
> >
> > datastore,
> > > and the augment applied only in those datastores where the result is
> true?
> >
> > Yes.
>
> But then it cannot be guaranteed that the schema for <operational> is a
> superset
> of the schema of configuration datastores - the when expression can
> evaluate to
> false in <operational> but true in <intended>.
>
>

I see your point now.
The server has to evaluate the when-stmts in operational.
Even though the schema trees are the same, the client has a complex task
comparing
<intended> to <operational>.  However it is no different than the existing
complexity comparing <candidate> to <running>.

> Lada
>
>
Andy

> >
> > > RFC 7950 says in sec. 7.21.5 that the context node for XPath
> evaluation is
> >
> > "the
> > > augment's target node in the data tree", but with NMDA we have
> multiple data
> > > trees, hence multiple target nodes.
> >
> > We had multiple datastores even before NMDA.  The when expression
> > could be true in candidate but false in running.
> >
> > /martin
> --
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
>
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