Re: [netmod] Adding a pre-existing leaf into a new 'choice' - NBC change?

[Andy Bierman <[e-mail]>]

On Fri, Nov 23, 2018 at 5:37 AM Robert Wilton <[e-mail]> wrote:

>
> On 23/11/2018 13:29, Ladislav Lhotka wrote:
> > On Fri, 2018-11-23 at 13:39 +0100, Juergen Schoenwaelder wrote:
> >> On Fri, Nov 23, 2018 at 01:02:03PM +0100, Ladislav Lhotka wrote:
> >>>> Here is an attempt to rewrite things in a way according to how I
> >>>> understand things works. It should be possible to describe what we
> >>>> mean. If we can't do that, we have a bigger problem. (I have changed
> >>>> only the last two sentences.)
> >>>>
> >>>> OLD
> >>>>
> >>>>     The leafref built-in type is restricted to the value space of some
> >>>>     leaf or leaf-list node in the schema tree and optionally further
> >>>>     restricted by corresponding instance nodes in the data tree.  The
> >>>>     "path" substatement (Section 9.9.2) is used to identify the
> referred
> >>>>     leaf or leaf-list node in the schema tree.  The value space of the
> >>>>     referring node is the value space of the referred node.
> >>>>
> >>>> NEW
> >>>>
> >>>>     The leafref built-in type is restricted to the value space of some
> >>>>     leaf or leaf-list node in the schema tree and optionally further
> >>>>     restricted by corresponding instance nodes in the data tree.  The
> >>>>     "path" substatement (Section 9.9.2) is used to identify a leaf or
> >>>>     leaf-list node in the data tree. The value space of the leafref
> >>>>     node is determined by the value space of the schema tree node
> >>> The term "value space of a schema tree node" is not defined.
> >> OK. So we say 'the value space of the type of the schema tree node'.
> > Yes, this is better. But what if the schema tree node is made invalid
> due to a
> > failed "when" expression? Does it still apply?
>
> I might be being picky, but it isn't absolutely clear from the text
> which node "schema tree node" refers to.
>
> Hence I wonder whether it might be better to say "...identify the
> referenced leaf or leaflist ..." and "value space of the referenced
> schema tree node".
>
>

IMO the RFC has a lot of room for improvement in this area:

 - the term "data node" is never defined but used 47 times
 - the term "data node identifier" is not defined or used
 - the term "schema node identifier" is defined and used 14 times
   (defined in sec. 3 Terminology and again in sec. 6.5)
 - every statement that uses some sort of path identifier (e.g. 9.9.2)
needs to clearly specify
   whether the syntax is based on schema-node identifier or data-node
identifier



> Thanks,
> Rob
>
>

Andy



>
> >
> >>
> >>>>     definining the referenced data tree node.
> >>> With require-instance=false there needn't be any referenced data tree
> node.
> >> So we add "(irrespective whether the node exists or not).
> > If the data tree node doesn't exist, we cannot refer to the schema tree
> node
> > that defines it.
> >
> >>>> This likely is not perfect yet but perhaps we manage to make it
> >>>> perfect. ;-) What is not yet clearly described I think is what
> >>>> 'further restricted by corresponding instance nodes in the data tree'
> >>>> means (and that I think depends on require-instance). Perhaps add
> >>> Right. In this case it is not "further restricted" but rather there is
> a
> >>> discrete set of possible values.
> >> A discrete set of possible values is a restriction so I do not
> >> understand your comment. So here is the next iteration:
> > If required-instance is true, there is no need to care about all this
> tricky
> > stuff with schema tree nodes and their types. In other words:
> >
> > 1. if required-instance = true, the permitted values are obtained from
> the data
> > tree.
> >
> > 2. if required-instance = false, the corresponding schema node has to be
> > determined, and its type defines the permitted values of the leafref
> node.
> >
> > It is an exclusive-or, #1 is not an "optional further restriction".
> >
> > Lada
> >
> >> NEW:
> >>
> >>      The leafref built-in type is restricted to the value space of some
> >>      leaf or leaf-list node in the schema tree and optionally further
> >>      restricted by corresponding instance nodes in the data tree (see
> >>      Section 9.9.3).  The "path" substatement (Section 9.9.2) is used
> >>      to identify a leaf or leaf-list node in the data tree. The value
> >>      space of the leafref node is determined by the value space of the
> >>      type of the schema tree node definining the referenced data tree
> >>      node (irrespective whether the referenced data tree node exists or
> >>      not).
> >>
> >> /js
> >>
>
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