Re: [netmod] Proposal to enhance the YANG tree output

Lou Berger <lberger@labn.net> Tue, 19 September 2017 14:22 UTC

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To: Robert Wilton <rwilton@cisco.com>, Martin Bjorklund <mbj@tail-f.com>
Cc: netmod@ietf.org
References: <20170919.132947.358857445863848356.mbj@tail-f.com> <990b8722-7a48-46ce-3f5d-96bc5cb66075@labn.net> <3734864d-9b27-7f61-c638-fd7c656c3692@cisco.com> <20170919.154728.285206235172744617.mbj@tail-f.com> <4f17fbca-6282-6b27-b390-9b85779e96da@cisco.com>
From: Lou Berger <lberger@labn.net>
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Date: Tue, 19 Sep 2017 10:22:16 -0400
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Subject: Re: [netmod] Proposal to enhance the YANG tree output
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On 9/19/2017 9:55 AM, Robert Wilton wrote:
>
> On 19/09/2017 14:47, Martin Bjorklund wrote:
>> Robert Wilton <rwilton@cisco.com> wrote:
>>> On 19/09/2017 14:28, Lou Berger wrote:
>>>> On 9/19/2017 7:29 AM, Martin Bjorklund wrote:
>>>>> Lou Berger <lberger@labn.net> wrote:
>>>>>> Martin,
>>>>>>
>>>>>> Speaking as a contributor:
>>>>>>
>>>>>>
>>>>>> On 9/15/2017 7:40 AM, Martin Bjorklund wrote:
>>>>>>> Robert Wilton <rwilton@cisco.com> wrote:
>>>>>>>> On 15/09/2017 11:21, Ladislav Lhotka wrote:
>>>>>>>>> Andy Bierman píše v Čt 14. 09. 2017 v 08:43 -0700:
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Actually I liked the early pyang output that was concise and easy to
>>>>>>>>>> remember.
>>>>>>>>>> The current format gets very cluttered and there are too many little
>>>>>>>>>> symbols
>>>>>>>>>> to remember them all.
>>>>>>>>> I agree.
>>>>>>> Me too.  The current draft adds three new magic symbols: "mp" "@" and
>>>>>>> "/".
>>>>>>>
>>>>>>> "mp" is for a mount point, and it can be generated directly from the
>>>>>>> YANG modules.
>>>>>>>
>>>>>>> Directly under a "mp", "/" and "@" are used to indicate that a node is
>>>>>>> mounted
>>>>>>> or available through a parent reference, respectively.
>>>>>>>
>>>>>>> I actually question the usability of "/" and "@".
>>>>>> I agree that / and @ are something new, and enabled by schema mount.
>>>>>> There have been repeated comments in the RTG WG that there needs to be
>>>>>> some way for vendors to convey what they have implemented with Schema
>>>>>> mount
>>>>> If that's the requirement, using the tree diagram is probably not the
>>>>> best way.  The tree diagram is intended to provide an overview of a
>>>>> given (set of) YANG module(s).
>>>>>
>>>>> A perhaps better way to convey the information is to create a file
>>>>> with an instantiated /schema-mounts tree.
>>>> using what syntax?  JSON and XML really isn't that easy for the
>>>> (human)
>>>> reader to parse.
>>> Perhaps there needs to be multiple versions of the generated tree
>>> output?
>>>
>>> 1) A normative tree diagram that shows the structure of the model.
>>> 2) A subsequent example that demonstrates what it looks like with the
>>> schema mounted modules.  Within the confines of a text document, the
>>> tree format still seems like a reasonable way to illustrate this, and
>>> I would say it is preferable to the verbosity of JSON or XML.
>>>
>>> I note that RFC 8022 includes an overview tree model in section 4 with
>>> some branches pruned, and then the complete representation in an
>>> appendix, which seems like a pragmatic approach.
>> Sure, but the question is about what special symbols we define.  Do we
>> need the extra symbols "/" and "@", and do we agree on what they mean?
> If we agree that tree style output is OK to illustrate the use of schema 
> mount, then I think that draft-ietf-netmod-yang-tree-diagrams could 
> define them, but indicate that they are only used to illustrate how 
> schema mount is used, and would not be seen in a regular YANG tree 
> diagram illustrating the structure of a YANG module.  

This seems like a reasonable compromise to me, and not a major change to
the draft.

Martin, what do you think?

Lou

> The alternative 
> might be that the RFCs that uses them defines what '/' and '@' mean for 
> that specific example.
>
> As for what the precise definition of '/' and '@' should be, I'm not 
> sure.  I think that you and Lou have a better handle on that ;-)
>
> Thanks,
> Rob
>
>
>>
>> /martin
>