Xufeng Liu <[email protected]> wrote:
> Hi,
> 
> > -----Original Message-----
> > From: Martin Bjorklund [mailto:[email protected]]
> > Sent: Friday, February 3, 2017 10:32 AM
> > To: Xufeng Liu <[email protected]>
> > Cc: [email protected]; [email protected];
> > [email protected]
> > Subject: Re: [i2rs] Kathleen Moriarty's No Objection on
> > draft-ietf-i2rs-yang-l3-
> > topology-08: (with COMMENT)
> > 
> > Hi,
> > 
> > 
> > Xufeng Liu <[email protected]> wrote:
> > > Hi Kent,
> > >
> > > > -----Original Message-----
> > > > From: Kent Watsen [mailto:[email protected]]
> > > > Sent: Thursday, February 2, 2017 8:39 PM
> > > > To: Xufeng Liu <[email protected]>
> > > > Cc: [email protected]; [email protected]
> > > > Subject: Re: [i2rs] Kathleen Moriarty's No Objection on
> > > > draft-ietf-i2rs-yang-l3-
> > > > topology-08: (with COMMENT)
> > > >
> > > > [reducing distribution]
> > > >
> > > >
> > > > Hi Xufeng,
> > > >
> > > > > Assume the following model:
> > > > >
> > > > > +--rw nodes
> > > > >   +--rw node [id]
> > > > >      +--rw id   string
> > > > >      +--rw under-lay-attribute-a ???
> > > > > +---ro nodes-state
> > > > >   +--ro node [id]
> > > > >      +--ro id   string
> > > > >      +--ro attribute-a string
> > > > >
> > > > > I cannot define the under-lay-attribute-a to reference attribute-a as:
> > > > >               type leafref {
> > > > >                 path "../node/attribute-a"'
> > > > >               }
> > > >
> > > >
> > > > True, but maybe it could be:
> > > >
> > > >    type leafref {
> > > >       path "../node/attribute-a"
> > > >       require-instance false;
> > > >       description
> > > >         "In the case when the referenced instance is not a configured
> > > >          object, the system may resolve it by looking for it under the
> > > >          /nodes-state node.  As the referenced operational state data
> > > >          may have a lifecycle independent of configuration, this results
> > > >          in an effect much like pre-provisioning interfaces in RFC
> > > >          7223.";
> > > >    }
> > > [Xufeng] I think that "require-instance false" does not help here. The
> > > validation for path "../node/attribute-a" still fails because
> > > "attribute-a" does not exist under /nodes/node/.
> > 
> > No, "require-instance false" essentially turns off validation.
> > Section
> > 9.9.3 in RFC 7950 says:
> > 
> >    If "require-instance" is "false", it means that the instance being
> >    referred to MAY exist in valid data.
> > 
> [Xufeng] My understanding is that this section talks about instance
> "data" validation, but I was talking about schema validation. The path
> statement is pointing to a non-existing schema node.

Aha, ok.  Yes, the path needs to refer to a valid schema node.  So the
path would be /nodes-state/node/attribute-a.

> At least, pyang,
> yangdump, and yangvalidator all fail on this currently.


/martin

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