Juergen Schoenwaelder <j.schoenwael...@jacobs-university.de> writes: > On Tue, May 29, 2018 at 03:58:33PM +0000, Kent Watsen wrote: >> [resurrecting this thread] >> >> Currently the zerotouch draft has a normative reference to this draft. >> I will this week post an update to the zerotouch draft to resolve the >> netconf list thread "a couple zerotouch-21 issues". It would be easy >> for me to also switch back to using rc:yang-data, but I won't do so if >> this draft remains an active work-in-progress. >> >> Please see below for more. >> >> >> On Wed, 2018-05-02 at 11:36 +0200, Juergen Schoenwaelder wrote: >> >On Wed, May 02, 2018 at 11:25:06AM +0200, Martin Bjorklund wrote: >> >> >> >> The primary use case is not "generic RPC messages", but standalone >> >> instance documents, error-info structures, etc. >> > >> > The proper solution for rpcs and actions is to define error >> > information as part of the rpc/action. YANG 1.1 does not support >> > this but this is where it should be fixed. >> >> Agreed, but note that the subscribed-notifications draft (both the >> published -12 and unpublished -13) are relying on being able to do >> just this, and YANG-next is years away... > > There is a description statement. > >> > Standalone instance documents (not tied to datastores) may have their >> > use cases as well but it feels odd to create support for standalone >> > instance documents as extensions and then to create even more >> > extensions to support augmentation of these instance documents and >> > whoever knows what comes next. >> >> What feels "odd" about this? Is it not using the extension statement >> as it was intended?
It is odd because RFC 7950 uses a lot of text to specify the special context and then the extension attempts to remove parts of this context (IMO incompletely). It would be much more logical to have a simple context-agnostic YANG spec and then use extensions for adding context-specific stuff. Somebody who is only interested in this "yang-data" usage of YANG still has to read all the nice CLRs in 7950 that only make sense for NETCONF. > > For me, extensions that define new data definition statements are > borderline. RFC 7950 has this nice statement: It is no borderline. The exception explicitly redefines YANG semantics in its description. > > o extension: An extension attaches non-YANG semantics to statements. > The "extension" statement defines new statements to express these > semantics. > > This does not help since we lack a definition for 'non-YANG semantics' > and yes I know that yang-data is today defined as an extension. But > for me, this is a hack and instead of creating a slightly more > generalized version of this hack, I prefer to stick to yang-data in > favor of a proper solution as part of YANG. > >> > For short-term needs, there is yang-data defined in RFC 8040. >> >> To be clear, the "short-term needs" are: >> >> a) zerotouch: to define a standalone instance document >> b) notification-messages: to define a new notification message >> c) subscribed-notifications: to define error-info structures >> >> As I recall, this draft (not RFC 8040) is needed: >> >> - for (a), because rc:yang-data doesn't support a top-level >> "choice" statement spanning "container" statements. > > So create a container. > >> - for (b), in order to augment a base yang-data "message" >> structure with additional nodes. > > So you are creating another augmentation mechanism. I am concerned > about ending up with a zoo of different mechanisms if we go down this > path, we may end up with every project or vendor creating their own > variants. > > With NMDA in place, YANG 1.1 is decribing schemas for datastores plus > operations and notifications. It is not a protocol message description > language or a standalone file format description language. If this is > needed, I prefer to create YANG X.Y - and if we manage the complexity > we have something that is ideally integrated and consistent. > >> - AFAIAA, RFC 8040 is sufficient for (c) >> >> Has anything changed? I don't think that we can un-adopt this >> draft with said dependencies, right? > > I am just voicing my opinion. It may very well be that the WG prefers > to go the route of not touching YANG 1.1 and instead patching around > its limitations with extensions. > > My concern is simply driven that some want to patch in via extensions > support for describing protocol messages and standalone documents, > others want to patch via extensions and updates a different versioning > system, and who knows what comes next. In the long run, I am afraid > this will become a mess. And yes, it is always difficult to predict > the future - we need crystal balls. Perhaps as an extension. ;-) And, luckily, vendors probably haven't yet realized the potential of extensions for creating proprietary YANG silos. This document should be very instructive for them. Lada > > /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 -- Ladislav Lhotka Head, CZ.NIC Labs PGP Key ID: 0xB8F92B08A9F76C67 _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
