Re: [netmod] References to the "tags" typedef

["Rob Wilton (rwilton)" <[e-mail]>]

> -----Original Message-----
> From: Christian Hopps <[e-mail]>
> Sent: 04 October 2019 10:18
> To: Rob Wilton (rwilton) <[e-mail]>
> Cc: Christian Hopps <[e-mail]>; Mahesh Jethanandani
> <[e-mail]>; [e-mail]
> Subject: Re: [netmod] References to the "tags" typedef
> 
> 
> 
> > On Oct 4, 2019, at 4:17 AM, Rob Wilton (rwilton) <[e-mail]>
> wrote:
> >

[RW] snipped.
> > There are a few solutions:
> >
> > 1) Split ietf-module-tags into a ietf-module-tags-types.yang that only
> > defines the typedef and the extension, and hence the
> > ietf-module-tags.yang only defines the module-tags container, and
> > ietf-yang-packages.yang can just import ietf-module-tags-types.yang
> > 2) Have ietf-yang-package.yang define its own "tags" type, hence there
> is no dependency on "ietf-module-tags.yang" at all.
> > 3) Tweak the schema specification for simplified-inline-schema in
> instance-data documents so that the use of ietf-module-tags.yang module
> effectively becomes "import-only" rather than "implemented".
> 
> If there's a problem here it doesn't seem to be with module tags, but more
> generically with this "pulling in" issue you have with instance data
> documents.
[RW] 
I agree that this is a generic issue.


 Are we now going to require *all* YANG types be defined in
> their own modules so their re-use in instance data documents doesn't "pull
> in" the other stuff? Are we going to go back and revise and republish all
> current YANG modules splitting them up this way?
[RW] 
I don't know.

I don't particularly like the "implemented" vs "import-only" behaviour in YANG.  This is partly because the information about whether a module needs to be implemented, or is an "import only" dependency isn't contained within YANG import statement.  Partly this is because to use identities the server must implement the module.  Partly this is because it is possible to "import-only" multiple revisions of a YANG module (which sort of seems strange, and perhaps also an unwanted complexity).

I also know that when OpenConfig were trying to reuse some of the IETF definitions they got stuck.
They wanted to use "iana-if-types.yang", but that has an import dependency on "ietf-interfaces.yang" which they didn't really want, but needed to import the "if:interface-type" base identity, which probably then requires that "ietf-interfaces.yang" is implemented.  Possibly the "interface-type" identity shouldn't have been defined in "ietf-interfaes.yang" at all.  Maybe it should have been part of "iana-if-types.yang" or perhaps a separate "ietf-interfaces-types.yang", or maybe the tight dependency is fine.
 
Hence, I'm not convinced that mixing type definitions and data node definitions in the same module is necessarily a good idea.  I'm not proposing that we go back and change what we have already done, but I'm also not convinced that the YANG modularity is really working as well as one might hope.

Thanks,
Rob


> 
> Thanks,
> Chris.
> 
> 
> 
> > 4) Don't worry about the fact that the file schema for a YANG package
> contains more than it should.
> >
> > I strongly dislike (4) as an option.
> > But I think that probably either (2) or (3) would be OK as a solution.
> >
> > Hence, it is probably not necessarily to split ietf-module-tags.yang
> into two files, because there are other solutions available.  It isn't
> even clear to me that (1) is necessarily the best solution anyway ...
> >
> > Thanks,
> > Rob
> >
> >
> >>
> >> Thanks,
> >> Chris.
> >>
> >>>
> >>>>
> >>>> (2) Have the package draft define its own "package tag" typedef,
> >>>> and
> >> not have an import reference on module-tags at all.  Probably if we
> >> do keep package tags, then we should also consider a mechanism by
> >> which they can be updated on a device equivalently to module tags.
> >>>>
> >>>> I'm currently thinking that the second choice might be a better
> >> approach at this time, but wanted to check whether you or the WG had
> >> an opinion.
> >>>>
> >>>> Thanks,
> >>>> Rob
> >>>>
> >>>>
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: netmod <[e-mail]> On Behalf Of Christian
> >>>>> Hopps
> >>>>> Sent: 25 September 2019 17:19
> >>>>> To: [e-mail]
> >>>>> Subject: Re: [netmod] I-D Action:
> >>>>> draft-ietf-netmod-module-tags-09.txt
> >>>>>
> >>>>> This adds the deprecated non-NMDA state module.
> >>>>>
> >>>>> Thanks,
> >>>>> Chris.
> >>>>>
> >>>>>> On Sep 25, 2019, at 12:15 PM, [e-mail] wrote:
> >>>>>>
> >>>>>>
> >>>>>> A New Internet-Draft is available from the on-line
> >>>>>> Internet-Drafts
> >>>>> directories.
> >>>>>> This draft is a work item of the Network Modeling WG of the IETF.
> >>>>>>
> >>>>>>     Title           : YANG Module Tags
> >>>>>>     Authors         : Christian Hopps
> >>>>>>                       Lou Berger
> >>>>>>                       Dean Bogdanovic
> >>>>>> 	Filename        : draft-ietf-netmod-module-tags-09.txt
> >>>>>> 	Pages           : 18
> >>>>>> 	Date            : 2019-09-25
> >>>>>>
> >>>>>> Abstract:
> >>>>>> This document provides for the association of tags with YANG
> modules.
> >>>>>> The expectation is for such tags to be used to help classify and
> >>>>>> organize modules.  A method for defining, reading and writing a
> >>>>>> modules tags is provided.  Tags may be registered and assigned
> >>>>>> during module definition; assigned by implementations; or
> >>>>>> dynamically defined and set by users.  This document also
> >>>>>> provides guidance to future model writers; as such, this document
> >>>>>> updates
> >> RFC8407.
> >>>>>>
> >>>>>>
> >>>>>> The IETF datatracker status page for this draft is:
> >>>>>> https://datatracker.ietf.org/doc/draft-ietf-netmod-module-tags/
> >>>>>>
> >>>>>> There are also htmlized versions available at:
> >>>>>> https://tools.ietf.org/html/draft-ietf-netmod-module-tags-09
> >>>>>> https://datatracker.ietf.org/doc/html/draft-ietf-netmod-module-ta
> >>>>>> gs
> >>>>>> -09
> >>>>>>
> >>>>>> A diff from the previous version is available at:
> >>>>>> https://www.ietf.org/rfcdiff?url2=draft-ietf-netmod-module-tags-0
> >>>>>> 9
> >>>>>>
> >>>>>>
> >>>>>> 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.
> >>>>>>
> >>>>>> Internet-Drafts are also available by anonymous FTP at:
> >>>>>> ftp://ftp.ietf.org/internet-drafts/
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>> netmod mailing list
> >>>>>> [e-mail]
> >>>>>> https://www.ietf.org/mailman/listinfo/netmod
> >>>>>>
> >>>>
> >>>> _______________________________________________
> >>>> netmod mailing list
> >>>> [e-mail]
> >>>> https://www.ietf.org/mailman/listinfo/netmod
> >>>
> >>> Mahesh Jethanandani
> >>> [e-mail]