Re: [netmod] [Technical Errata Reported] RFC7950 (6031)

Martin Björklund <mbj+ietf@4668.se> Fri, 03 April 2020 13:54 UTC

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Date: Fri, 03 Apr 2020 15:54:21 +0200 (CEST)
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To: jason.sterne@nokia.com
Cc: rwilton=40cisco.com@dmarc.ietf.org, j.schoenwaelder@jacobs-university.de, mbj+ietf@4668.se, warren@kumari.net, netmod@ietf.org, rfc-editor@rfc-editor.org
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Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
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Hi,

"Sterne, Jason (Nokia - CA/Ottawa)" <jason.sterne@nokia.com> wrote:
> I don't think we should allow overwriting a require-instance true with
> a require-instance false in a derived type. It seems to go against the
> spirit of avoiding expansion of allowable values.

As I wrote earlier in this thread, the value space doesn't change with
require-instance.


/martin



> 
> From section 4.1 of RFC7950:
> 
>         Derived types can restrict their base type's set of valid values
> 
> And this text in section 7.3.4 implies that derived types only do
> further restriction:
> 
>     If the type's default value is not valid according to the new
>    restrictions specified in a derived type or leaf definition, the
>    derived type or leaf definition MUST specify a new default value
>    compatible with the restrictions.
> 
> Going the other direction (overwriting with require-instance true)
> seems OK to me.
> 
> Jason
> 
> 
> > -----Original Message-----
> > From: netmod <netmod-bounces@ietf.org> On Behalf Of Rob Wilton
> > (rwilton)
> > Sent: Friday, April 3, 2020 8:06 AM
> > To: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>de>;
> > Martin
> > Björklund <mbj+ietf@4668.se>
> > Cc: warren@kumari.net; netmod@ietf.org; rfc-editor@rfc-editor.org
> > Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: netmod <netmod-bounces@ietf.org> On Behalf Of Juergen
> > Schoenwaelder
> > > Sent: 27 March 2020 16:13
> > > To: Martin Björklund <mbj+ietf@4668.se>
> > > Cc: ibagdona@gmail.com; warren@kumari.net; netmod@ietf.org; rfc-
> > > editor@rfc-editor.org
> > > Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
> > >
> > > On Fri, Mar 27, 2020 at 04:35:44PM +0100, Martin Björklund wrote:
> > > > [re-sent w/ correct address]
> > > >
> > > > Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> wrote:
> > > > > Hi,
> > > > >
> > > > > two comments:
> > > > >
> > > > > - It is unclear to me whether this really qualifies as an errata.
> > > > >
> > > > > - If we add this, then there should probably text about which
> > > > >   combinations are allowed. For example, for pattern and ranges, there
> > > > >   is explicit text that says further restrictions of the value space
> > > > >   are possible, bot not expansions. If we follow that logic, then
> > > > >
> > > > >   typedef a {
> > > > >     type leaf-ref {
> > > > >       path "/some/thing";
> > > > >       require-instance true;
> > > > >     }
> > > > >   }
> > > > >
> > > > >   typedef b {
> > > > >     type a {
> > > > >       require-instance false;
> > > > >     }
> > > > >   }
> > > > >
> > > > >   might be illegal since b has a larger value space than a.
> > > >
> > > > The value space of b is the same as for a. "require-instance" doesn't
> > > > change the value space; it changes semantic validation of the given
> > > > values ((see my mail from 17 Mar, "Require-instance problem").
> > > >
> > > > /martin
> > >
> > > OK. If we consider require-instance a constraint and not a
> > > restriction,
> > > then the motivation for this errata is at least
> > > confusing:
> > >
> > >   Since no one argued against this understanding, this errata changes
> > >   the text to the same form as in other restrictions applicable to
> > >   derived types.
> > >
> > > Simply put: Do you think it is OK to overwrite a require-instance true
> > > with a require-instance false in a derived type?
> > [RW]
> > I'm not sure, but going in the other direction seems plausible.
> > 
> > E.g. you start with a typedef that is explicitly require-instance
> > false that is then
> > refined by a typedef to be require-instance true.
> > 
> > Regards,
> > Rob
> > 
> > 
> > >
> > > /js
> > >
> > > --
> > > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > > Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
> > > Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>
> > >
> > > _______________________________________________
> > > netmod mailing list
> > > netmod@ietf.org
> > > https://www.ietf.org/mailman/listinfo/netmod
> > 
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