Re: [netmod] Fwd: New Version Notification for draft-ietf-netmod-yang-instance-file-format-01.txt

[Balázs Lengyel <[e-mail]>]

On 2019. 02. 07. 13:10, Robert Wilton wrote:

Hi Balazs,

Regarding identifying the instance data using a YANG package.

If the YANG packages work is liked by the WG and progresses, then it seems plausible that a YANG package could become a better way of identifying the set of modules rather than using YANG library for a couple of reasons:
 1) It will allow modules to be identified via semantic version rather than just revision date.  This will likely be more meaningful to readers.

BALAZS: The nice thing about using yang-library is that when the semver work augment the library with the module-version it will be available for instance-data for free.

 2) It allows for a much more concise definition.  Rather than having to try and infer what schema a particular set of YANG modules related to from the list of modules, it can instead refer to a single package definition and version number.

BALAZS: Using packages would be more, concise however in some cases you might not want to declare a package. E.g. we use a modular architecture where one design group might be responsible for only one YANG module (YAM). They need to deliver some instance-data related to that YAM, but they don't want to declare a package that contains just one YAM. Also some modules are packaged in so many ways that it is easier to define their instance data just for that module. So while packages are an interesting idea they will never completely replace the module level, hence we need a module level solution too. One packages are agreed, I will be happy to expand this specification.

 3) YANG library (certainly RFC7895bis) defines the schema in terms of the datastore, so if this version of YANG library is being used then it is a bit more confusing as to which datastore is being referred to.  I appreciate that there is a datastore leaf in the instance data that can help mitigate this.

I also note that the draft currently binds that the only allowed inline schema is YANG library, but that seems somewhat overly restrictive, and perhaps this could be loosened to a leaf-list of inline module@revision definitions?

BALAZS: IMHO ietf-yang-library contains ll the data we need in a well defined format (and some we don't always need). So why define a new format when we already have one. Also by using YANG library we get for free any new data in it e.g.module-version. We also need the info about leafs and deviations.

I also appreciate that you don't want to delay the instance data draft for YANG packages, bit I wonder whether the draft can easily facilitate using a YANG package definition in future if required.

BALAZS: As I agree with your comment about choice (see below) that a package reference can be easily included in that.

Hence, rather than using a union for the "target pointer", I wonder whether it wouldn't be better to use a choice statement instead.

E.g. the choice statement could be something like this:

 choice "schema"
   leaf-list inline {
     type string {
       pattern '\w+@\d{4}-\d{2}-\d{2}\.yang';
     }
   }
   leaf yang-library-ref { type uri } // Points to a instance data document YANG library content.
 }

In future, the package draft could then augment (or update the revision) with something like this :

   container package-ref {
     leaf "name" { type string; }
     leaf "version" { type yang-semver; }
     leaf-list "url" { type uri; } // Points to a instance data document containing YANG package content.
   }

BALAZS: OK, choice maybe a better choice because it is easier to extend and because it explicitly states the method used. So how about:

 choice "target-specification"
   leaf inline {
     type string { pattern 'ietf-yang-library@\d{4}-\d{2}-\d{2}\.yang'; }   // I still want to use the library 
   }
   leaf yang-library-ref { type uri } 
 }

Later we can augment this choice with container package-ref.

Thanks,
Rob

On 06/12/2018 10:15, Balázs Lengyel wrote:

Hello,

We uploaded a new version of the instance data draft. We tried to address all comments and also to rework the format chapter to make it easier to read. We omitted 2 comments:

Rob commented that YANG packages could be used for defining the target modules for instance data: I would like to avoid that because:

• Packages are not defined for YANG. Currently they are not part of the versioning solution even though they were discussed and are generally a good idea.
• IMHO as deviations/features are set on module level, just specifying packages would not be enough. If we start using package+module level deviations/features we may end up with a more complicated hybrid solution.
• Module level YANG target definitions as described in the draft are simple and need no new design
  

Jürgen stated that it would be better to use the YANG XML/JSON encoding as a format instead of referencing the get operation/request. I might even agree with him, but for 2 reasons I did not follow his idea:

• Currently there is no RFC I could reference either for XML or JSON. AFAIK even RFC7951 does not define how multiple modules should be encoded side by side.
• It is not the job of the instance data draft to dictate how to encode YANG data generally e.g. on the wire.
  
• The contents of the get operation/request are well defined
  

regards Balazs

-------- Forwarded Message --------

Subject:	New Version Notification for draft-ietf-netmod-yang-instance-file-format-01.txt
Date:	Thu, 6 Dec 2018 02:12:12 -0800
From:	[e-mail]
To:	Benoit Claise <[e-mail]>, Balazs Lengyel <[e-mail]>

A new version of I-D, draft-ietf-netmod-yang-instance-file-format-01.txt
has been successfully submitted by Balazs Lengyel and posted to the
IETF repository.

Name: draft-ietf-netmod-yang-instance-file-format
Revision: 01
Title: YANG Instance Data File Format
Document date: 2018-12-06
Group: netmod
Pages: 21
URL: https://www.ietf.org/internet-drafts/draft-ietf-netmod-yang-instance-file-format-01.txt" rel="nofollow">https://www.ietf.org/internet-drafts/draft-ietf-netmod-yang-instance-file-format-01.txt
Status: https://datatracker.ietf.org/doc/draft-ietf-netmod-yang-instance-file-format/" rel="nofollow">https://datatracker.ietf.org/doc/draft-ietf-netmod-yang-instance-file-format/
Htmlized: https://tools.ietf.org/html/draft-ietf-netmod-yang-instance-file-format-01" rel="nofollow">https://tools.ietf.org/html/draft-ietf-netmod-yang-instance-file-format-01
Htmlized: https://datatracker.ietf.org/doc/html/draft-ietf-netmod-yang-instance-file-format" rel="nofollow">https://datatracker.ietf.org/doc/html/draft-ietf-netmod-yang-instance-file-format
Diff: https://www.ietf.org/rfcdiff?url2=draft-ietf-netmod-yang-instance-file-format-01" rel="nofollow">https://www.ietf.org/rfcdiff?url2=draft-ietf-netmod-yang-instance-file-format-01

Abstract:
There is a need to document data defined in YANG models when a live
YANG server is not available. Data is often needed already in design
time or needed by groups that do not have a live running YANG server
available. This document specifies a standard file format for YANG
instance data, which follows the syntax and semantic from existing
YANG models, re-using existing formats from <get> operation/request
and decorates them with metadata.



Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

The IETF Secretariat

-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
Senior Specialist
Mobile: [phone]              email: [e-mail] 

_______________________________________________
netmod mailing list
[e-mail]
https://www.ietf.org/mailman/listinfo/netmod" rel="nofollow">https://www.ietf.org/mailman/listinfo/netmod

-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
Senior Specialist
Mobile: [phone]              email: [e-mail]