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

Robert Wilton <rwilton@cisco.com> Tue, 19 September 2017 13:55 UTC

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To: Martin Bjorklund <mbj@tail-f.com>
Cc: lberger@labn.net, 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>
From: Robert Wilton <rwilton@cisco.com>
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Date: Tue, 19 Sep 2017 14:55:19 +0100
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Subject: Re: [netmod] Proposal to enhance the YANG tree output
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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.  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