Re: [netmod] choice/case in tree diagrams

joel jaeggli <joelja@bogus.com> Tue, 06 March 2018 17:44 UTC

Return-Path: <joelja@bogus.com>
X-Original-To: netmod@ietfa.amsl.com
Delivered-To: netmod@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9649012895E for <netmod@ietfa.amsl.com>; Tue, 6 Mar 2018 09:44:32 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -6.91
X-Spam-Level:
X-Spam-Status: No, score=-6.91 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, T_RP_MATCHES_RCVD=-0.01] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GQIhsXPmu4fy for <netmod@ietfa.amsl.com>; Tue, 6 Mar 2018 09:44:30 -0800 (PST)
Received: from nagasaki.bogus.com (nagasaki.bogus.com [IPv6:2001:418:1::81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 261091270AC for <netmod@ietf.org>; Tue, 6 Mar 2018 09:44:30 -0800 (PST)
Received: from MBP.local (c-73-202-177-209.hsd1.ca.comcast.net [73.202.177.209]) (authenticated bits=0) by nagasaki.bogus.com (8.15.2/8.15.2) with ESMTPSA id w26HiR6m012333 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Tue, 6 Mar 2018 17:44:28 GMT (envelope-from joelja@bogus.com)
X-Authentication-Warning: nagasaki.bogus.com: Host c-73-202-177-209.hsd1.ca.comcast.net [73.202.177.209] claimed to be MBP.local
To: Lou Berger <lberger@labn.net>, Martin Bjorklund <mbj@tail-f.com>, vladimir@transpacket.com
Cc: netmod@ietf.org
References: <1520262414.7198.35.camel@nic.cz> <6a1ed43f-398b-4538-52aa-d7f8c219047e@tail-f.com> <c9a60629-a1de-0b5b-77a0-595f614bcad8@transpacket.com> <20180306.104411.829341372037212681.mbj@tail-f.com> <161fb126c00.27d3.9b4188e636579690ba6c69f2c8a0f1fd@labn.net>
From: joel jaeggli <joelja@bogus.com>
Message-ID: <ea01ba05-6f93-f553-b585-29c679d21007@bogus.com>
Date: Tue, 6 Mar 2018 09:44:22 -0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.6.0
MIME-Version: 1.0
In-Reply-To: <161fb126c00.27d3.9b4188e636579690ba6c69f2c8a0f1fd@labn.net>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/jeyGdlIiAB8IIzRbrn4QKDrfUcM>
Subject: Re: [netmod] choice/case in tree diagrams
X-BeenThere: netmod@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: NETMOD WG list <netmod.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/netmod>, <mailto:netmod-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/netmod/>
List-Post: <mailto:netmod@ietf.org>
List-Help: <mailto:netmod-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/netmod>, <mailto:netmod-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 06 Mar 2018 17:44:33 -0000


On 3/6/18 3:29 AM, Lou Berger wrote:
> Martin,
>
>
> On March 6, 2018 4:44:47 AM Martin Bjorklund <mbj@tail-f.com> 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.
>>
>
> I agree.
I would tend to err on that side  as well it's a little late for that.
>> 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>:
>>
> I think we should match current tooling/practice here as well. Can you
> confirm how pyang works today?
>
> My memory is no such space is added.  If my memory is correct, my
> preference is to change the text rather then the tooling.
>
> Lou
> (As contributor)
>
>>      <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 <vladimir@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.schoenwaelder@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
>