I finally caught up to this thread. I agree with concerns raised by Radek and 
Balazs, but as others have mentioned an errata doesn’t seem to be the right 
medium for this. OTOH, yang-next might be too far away…. Could we do an update 
to RF7950 just for this? I realize it’s lots of work/overhead for “just” this 
issue.

Regards,
Reshad.

From: netmod <[email protected]> on behalf of Kent Watsen 
<[email protected]>
Date: Thursday, April 23, 2020 at 12:59 PM
To: 'Andy Bierman' <[email protected]>
Cc: "[email protected]" <[email protected]>, "Rob Wilton (rwilton)" 
<[email protected]>
Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)

The consensus seems to be that:
  - the errata should be rejected
        - Rob, do you agree?
  - YANG-next should fix it later
        - I created https://github.com/netmod-wg/yang-next/issues/104
  - implementations should try to do the right thing now
        - Radek’s suggestion below LGTM!


Tallies:
   - for reject: Andy, Martin, Juergen, and Kent
   - for accept: Radek, and Balazs
   - unclear: Lada, Rob, and Jason


Kent // as co-chair



On Apr 14, 2020, at 10:35 AM, Andy Bierman 
<[email protected]<mailto:[email protected]>> wrote:

Hi,

I agree with Juergen that this errata should be rejected and the issue resolved 
in yang-next.
No IETF module should use this construct. It is easy to convert to an 
equivalent form that is not under dispute.


Andy


On Tue, Apr 14, 2020 at 6:40 AM Radek Krejci 
<[email protected]<mailto:[email protected]>> wrote:
Hi,
Dne 09. 04. 20 v 17:26 Kent Watsen napsal(a):



On Apr 6, 2020, at 3:42 AM, Juergen Schoenwaelder 
<[email protected]<mailto:[email protected]>>
 wrote:

The definition I found in RFC 8639 is this:

       leaf stream {
         type stream-ref {
           require-instance false;
         }
         mandatory true;
         description
           "Indicates the event stream to be considered for
            this subscription.";
       }

This could be changed to:

       leaf stream {
         type leafref {
    path "/sn:streams/sn:stream/sn:name";
           require-instance false;
         }
         mandatory true;
         description
           "Indicates the event stream to be considered for
            this subscription.";
       }


I can confirm that `yanglint` validates the module cleanly after this change.



On Apr 6, 2020, at 7:38 AM, Martin Björklund 
<[email protected]<mailto:[email protected]>> wrote:

I think the correct fix is to change the text so that
"require-instance" is not classified as a restriction and keep the
default.

Agreed.



Also, I think that it would be easiest (for backwards
compatibility w/ existing models) to allow "require-inetance" to be
changed in derived types.

However, this cannot imo be done in an errata.

While I appreciate Radek and Michal’s perspective, I also think that is would 
be best for the community for `yanglint` to support this, as they are published 
modules doing it.


I don't feel as an expert for IETF processes, so I don't know if this issue can 
be solved in errata or not (and I'm not sure there is a consensus on this in 
mailing list). For the implementation, I would appreciate at least a consensus 
on a solution. So far I saw opinions to allow it, to disallow and also to make 
it implementation-specific (which means in fact to disallow from the authors 
perspective, since there can be a tool disallowing it and we are saying that 
such a tool is ok). So, there is no clear way for implementors, which means 
problems for interoperability - there will be always someone unhappy and so far 
I don't know what is the major opinion to go.

So far, I tend to allow it (accept by libyang), but print warning to warn 
authors about possible problems (some tool can refuse such a module). Is it ok?

Radek



As an aside, I feel that all modules should be tested against all available 
validation tools during the publication process, but to find issues in the 
modules and well as possibly improve the tools.

Sadly, I only have `yanglint` and `yangson` available to me.  I just checked 
for the “yang validator” project, but both 
www.yangvalidator.com<http://www.yangvalidator.com/> and 
https://www.yangcatalog.org/yangvalidator seem to be down.


Kent // contributor


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