On Mon, Aug 24, 2015 at 12:20 PM, Randy Presuhn < [email protected]> wrote:
> Hi - > > >From: Ladislav Lhotka <[email protected]> > >Sent: Aug 24, 2015 11:44 AM > >To: Andy Bierman <[email protected]> > >Cc: "[email protected]" <[email protected]> > >Subject: Re: [netmod] Y26 again, sorry > ... > >> YANG does not provide any mechanism to REQUIRE modules A and B > >> to both be implemented on a server. You may think it should, but > >> currently the YANG conformance is for an individual module. > > > >There are sections on conformance and conformance announcement, > >and they say nothing like this. In my view, the data model comprises > >*all* modules advertised by the server. I think your interpretation > >of conformance might be an extrapolation from SNMP/SMI times, but, > >for better or worse, it really has no support in the YANG spec. > > It sounds as though you might be talking past each other. > I believe part of Andy's point is that clients will need to deal > with servers that do not implement (and thus do not advertise) > the augmenting module. But there's (I think) a more interesting > issue beneath this. > > Let's start with module M. Let's say M is for "modem" (to pick > an obsolete but widely understood resource). > Two different augmenting modules, F (for FSK - frequency > shift keying) and Q (for QAM - quadrature amplitude modulation) > are developed. Let us say that F and Q are mutually incompatible. > > A system with multiple Ms could well have both M+F and M+Q modems, > but (if we claim F & Q are incompatible) could not have M+F+Q. > If naked M is to be prohibited in systems (also) supporting F or Q > or both, we don't currently have a mechanism to do so. > > When I examine the module M, I have absolutely no way of knowing about F or Q. Where are the instructions to the developers that only M+F or M+Q is allowed, and never M or M+F+Q? Where would they go except M or a stand-alone document describing M+* ? If these instructions are not in M, F, or Q, then how will developers find it? It seems we would need a way to say that conformance to M is not meaningful. Only conformance to M+? is meaningful (where M can define the requirements for ?) > Randy > > Andy > _______________________________________________ > netmod mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/netmod >
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