Hi - >From: Ladislav Lhotka <[email protected]> >Sent: Sep 10, 2015 2:02 AM >To: Randy Presuhn <[email protected]>, [email protected] >Subject: Re: [netmod] Y26 again, sorry > >Randy Presuhn <[email protected]> writes: > >> Hi - >> >>> From: Andy Bierman >>> Sent: Sep 9, 2015 12:10 PM >>> To: Ladislav Lhotka >>> Cc: Robert Wilton , Randy Presuhn , "[email protected]" >>> Subject: Re: [netmod] Y26 again, sorry >> ... >>> I don't think it really addresses the design pattern very well. >>> You want to claim that M and Q are both being developed at the >>> same time,so it's OK that Q adds mandatory nodes to M. YANG >>> has no such rule.YANG says a server can implement M and never >>> implement Q.YANG says a server may implement M and then add Q >>> in a future release.These conformance mechanisms do not align >>> with your expectationsof how YANG can/should be used. >> >> I agree with Andy that there seems to be a mismatch in expectations. > >I wonder if we can explain these differences. Is your and Andy's >expectation that the configuration schema has to reflect actual hardware >configuration, perhaps even dynamically adjust to the changes?
I can't speak for Andy, but I would expect that a server's schema could change dynamically, as a result, for example, of new hardware or software being introduced into a running system. We were doing this in the late 1980's - it's one of the things that pulled us into the subagent technology space. >In my view, the supported (and advertised) data model and hardware >configuration of the device are two different things. They are different, but there are relationships. When a new line card is inserted, I would expect the system to acquire any necessary schema knowledge in order to manage that new resource. Likewise, if non-present hardware is being provisioned, part of that provisioning process (possibly implicit) is for the system being provisioned to acquire the necessary schema knowledge so that it can perform at least a preliminary validation of the provisioning data. >> Let's look at a slightly more complex hypothetical case to tease >> out how folks *want* things to work. Assume the following have >> been defined: >> >> - base module M >> - augmentation Q >> - augmentation R >> >> On a server claiming to supporting the modules containing M, Q, >> and R, respectively, which of the following might one encounter >> concurrently? >> >> - plain M >> - M+Q >> - M+R >> - M+Q+R > >It depends on what you mean by "encounter" but in terms of datastore >validity the only possible answer IMO is M+Q+R. By "encounter" I mean if a client asks the server for all of its Ms, and the server also supports Q and R, are all of the Ms *guaranteed* to be M+Q+R, or is it possible that some of the Ms might lack Q or lack R of lack both? If what netmod gives us is strictly M+Q+R, how would one model a system inhabited by a mixture of the four kinds of Ms? Randy _______________________________________________ netmod mailing list [email protected] https://www.ietf.org/mailman/listinfo/netmod
