On 3/6/2018 10:44 AM, Martin Bjorklund wrote:
Hi,

After thinking some more about this, realizing that this document is
in AUTH48, and looking at the first sentence in the Abstract:

    This document captures the current syntax used in YANG module tree
    diagrams.

I have reached the conclusion that we probably shouldn't make any
drastic changes.
Obviously, otherwise I send the document back to the WG.

Regards, Benoit

The current syntax, with flags for choice but not for case, may look a
bit odd, but it does follow RFC 7950 where a choice node can have a
config property, but case cannot.  Also, this syntax has now been used
for several years w/o causing much confusion.

I suggest the following changes to this document:

OLD:

        <flags> is one of:
          rw  for configuration data
          ro  for non-configuration data, output parameters to rpcs
              and actions, and notification parameters
          -w  for input parameters to rpcs and actions
          -u  for uses of a grouping
          -x  for rpcs and actions
          -n  for notifications
          mp  for nodes containing a "mount-point" extension statement

NEW:

        <flags> is one of:
          rw  for configuration data
          ro  for non-configuration data, output parameters to rpcs
              and actions, and notification parameters
          -w  for input parameters to rpcs and actions
          -u  for uses of a grouping
          -x  for rpcs and actions
          -n  for notifications
          mp  for nodes containing a "mount-point" extension statement

          case nodes do not have any <flags>.

Then, since the syntax requires whitespace before <name>:

      <status>--<flags> <name><opts> <type> <if-features>

we need to fix the examples:

OLD:

              +--rw (root-type)
                 +--:(vrf-root)

NEW:

              +--rw (root-type)
                 +-- :(vrf-root)

(two occurances)



/martin



Vladimir Vassilev <vladi...@transpacket.com> wrote:

On 03/05/2018 06:40 PM, Per Hedeland wrote:
On 2018-03-05 16:06, Ladislav Lhotka wrote:
On Mon, 2018-03-05 at 15:49 +0100, Per Hedeland wrote:
On 2018-03-05 15:41, Ladislav Lhotka wrote:
On Mon, 2018-03-05 at 15:26 +0100, Martin Bjorklund wrote:
Juergen Schoenwaelder <j.schoenwael...@jacobs-university.de> wrote:
On Mon, Mar 05, 2018 at 02:54:18PM +0100, Martin Bjorklund wrote:
So it seems the running code got it right. ;-)
As the author of that code, I think that was purely by accident...

But I'm not convinced it is the correct solution.  We have one example
in the other thread where someone was confused by the "rw" flag and
thought that it implied that the node would be present in the data
tree.

So what does rw mean?

(i)  The schema node has a rw property.
(ii) The schema node can be instantiated and the instantiated data
node
       has a rw property.

I think it is difficult to have both at the same time. If the tree is
a representation of schema nodes, then (i) seems to make more
sense. That said, the explanation in 2.6 is somewhat vague since it
says 'data' and not 'nodes' (like everywhere else):

OLD:

         <flags> is one of:
           rw  for configuration data
           ro  for non-configuration data, output parameters to rpcs
               and actions, and notification parameters

NEW:

         <flags> is one of:
           rw  for configuration data nodes
           ro for non-configuration data nodes, output parameters to
           rpcs
               and actions, and notification parameters
I think this is ok.  But that means that we also have to add:

             --  for a choice or case node

But in order to be consistent, we should probably have:

             --  for a choice, case, input or output node
But unlike the three other statements, "choice" can have the config
substatement, so "rw/ro" makes sense there.
I don't think so - that config statement does not a define a property
of
the choice node (it can obviously neither be read nor written), only a
default for descendant data nodes, as described in section 7.21.1 of
RFC
7950.
It is not a default - if a choice has "config false", then no
descendant can be
"config true". One of the benefits of having rw/ro in the ascii tree
is to see
where a state data subtree actually starts.
It is a default, but yes, it is also a restriction in the specific
case
of the argument being "false" at a point where the default would
otherwise be "true". And in that case it is equivalent to having
"config
false" on all the descendant data nodes, and they will of course be
flagged as "ro" regardless of whether the "config false" comes from
the
choice or the individual data nodes - and that is where the state
*data*
suntree(s) actually start(s).

So I guess the question then is whether this specific case motivates
always having flags on specifically choice nodes, while the other
non-data nodes have no flags. Since the 'config' statement is ignored
in
rpc/action input/output and notification, choice nodes there should
then
presumably have "-w"/"ro"/"-n". Personally I think the diagram is
clearer with flags only on the data nodes.
When I think about it <flags> do not have any information contents
outside of the context of a data tree and its schema. So if we are
removing clutter we should probably start there by specifying that
<flags> should be ommited under rpc,notification and action.

Vladlimir
--Per

Lada

--Per

Lada

This means that the correct tree syntax for choice and case will be:

       +-- (subnet)?
          +-- :(prefix-length)
          |  +--rw prefix-length?   uint8
          +-- :(netmask)
             +--rw netmask?         yang:dotted-quad


/martin


The document (as far as I searched for it) does not clearly say that
'node' means 'schema node'. In hindsight, it might have been useful to
explicitely import terminology from RFC 7950 and to use it carefully
(RFC 7950 has 'schema node' and 'data node' but here we largely talk
about 'nodes' - and my assumption is that this means 'schema nodes'.)
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
.


_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod

Reply via email to