Re: [netmod] yang-data-ext issues
Martin Bjorklund <mbj@tail-f.com> Mon, 23 April 2018 06:52 UTC
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Date: Mon, 23 Apr 2018 08:52:22 +0200
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] yang-data-ext issues
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Andy Bierman <andy@yumaworks.com> wrote: > On Wed, Apr 18, 2018 at 10:47 AM, Martin Bjorklund <mbj@tail-f.com> wrote: > > > Hi, > > > > Andy Bierman <andy@yumaworks.com> wrote: > > > On Wed, Apr 18, 2018 at 10:26 AM, Kent Watsen <kwatsen@juniper.net> > > wrote: > > > > > > > I like Andy's proposal below, for the argument of the 'yang-data' > > > > statement to encode some meta-information regarding the > > context/namespace > > > > in which it's used, but I wonder how it really works. For instance, > > would > > > > "top" and "error-info" be the only allowed base-path values for the > > > > argument? and what is the value of the remainder of the path? are we > > > > expecting for there to be some kind us 'uses' statement that can refer > > to > > > > just the base-path component to implement substitution-group like > > behavior? > > > > > > > > > > > > > > > > > > > > > If we want to avoid defining these contexts, then we could just define > > root > > > vs. nonroot. > > > > > > e,g: > > > > > > x:yang-data /mydef1 { > > > container foo; > > > } > > > > > > x:yang-data mydef2 { > > > leaf x; > > > leaf y; > > > container z; > > > } > > > > > > > > > Only an argument starting with '/' would be treated as a top-level data > > > node. > > > > > > All other yang-data definitions are not allowed to appear as a root node. > > > The context where this yang-data is used is completely proprietary. > > > The mechanism used to expand this yang-data as if it was a grouping > > > is completely proprietary. > > > > > > The augment-yang-data extension only applies to top-level yang-data > > > definitions. > > > > > > However, my preference is to only standardize top-level yang-data. > > > > What is "top-level" yang-data? > > > > > > > It is a data structure that represents an instance document. So then I assume that you also want to change the current draft -01 behavior so that a yang-data structure MUST have a single container as the child? Just like in rc:yang-data. > Since this is the ONLY definition of yang-data we have in the standard, > what is a yang-data definition that represents some unspecified usage, > other than an instance document? We want to create a flexible solution for creating structures that can be used in other places than just self-contained instance document. One example is the error-info data (see subscribed-notifications). > Why is this any different than a YANG grouping? ? We don't have these CLRs for groupings; the following is legal: grouping foo { leaf a { ... } leaf b { ... } } grouping bar { leaf b { ... } } It is up to the user of the grouping to ensure it is used in a way so that the result is legal. I think yang-data should work the same way. /martin > > > > > /martin > > > > > > > Andy > > > > > > I do not see any need for the other form since all functionality can be > > > achieved with a grouping and a proprietary YANG extension. > > > > > > Kent // contributor > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > > > > > > > > > On 4/16/18, 1:05 PM, "netmod on behalf of Andy Bierman" < > > > > netmod-bounces@ietf.org on behalf of andy@yumaworks.com> wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Apr 16, 2018 at 9:46 AM, Robert Wilton <rwilton@cisco.com> > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > On 16/04/2018 17:07, Andy Bierman wrote: > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Apr 16, 2018 at 8:44 AM, Robert Wilton <rwilton@cisco.com> > > wrote: > > > > > > > > Don't groupings have a somewhat similar concern? > > > > > > > > E.g. if two groupings define the same data node name and are used at > > the > > > > same point then you would get a namespace clash, but YANG does not > > disallow > > > > the groupings: > > > > > > > > > > > > grouping foo_widget { > > > > > > > > leaf name { > > > > > > > > type string; > > > > > > > > description "Name of my foo widget"; > > > > > > > > } > > > > > > > > } > > > > > > > > > > > > > > > > grouping bar_widget { > > > > > > > > leaf name { > > > > > > > > type string; > > > > > > > > description "Name of my bar widget"; > > > > > > > > } > > > > > > > > } > > > > > > > > > > > > > > > > container all_widgets { > > > > > > > > uses foo_widget; > > > > > > > > uses bar_widget; > > > > > > > > } > > > > > > > > > > > > The principal difference here, is that the compiler can easily check > > and > > > > reject the conflict at the uses statements. > > > > > > > > Hence I think that it would be good if we could find a solution for > > > > yang-data-ext that doesn't not require all root yang-data nodes to be > > > > unique, since that feels somewhat clunky. I.e. my preference is to > > keep > > > > them less restrictive, as Martin has proposed, if this is feasible. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > It is not clunky that 2 top-level YANG data nodes in the same module > > > > > > > > have unique names. This is simple and deterministic. > > > > > > > > This restriction has not been a problem so far. > > > > > > > > I agree with the statements above. > > > > > > > > But it is not clear to me that yang-data-ext is really defining new top > > > > level data nodes that are part of the same tree/namespace as the > > > > configuration/state nodes. In Martin's examples they were used within > > > > RPCs, and it the forcing the names to be unique in that context that I > > > > think would be clunky. E.g. in Martin's example forcing different > > names > > > > for "reason" and "user-info" doesn't seem to be helpful. > > > > > > > > > > > > > > > > > > > > > > > > > > > > The yang-data statement has to define the context or new abstract > > > > namespace, > > > > > > > > or whatever this hack is called. > > > > > > > > Perhaps. I think that this depends on how they are used. > > > > > > > > > > > > > > > > > > > > > > > > The yang-data statement has to specify the expansion point, or > > > > > > > > at least specify that it is or is not the top-level. > > > > > > > > > > > > > > > > yang-data top/name1 { > > > > > > > > container mydata; > > > > > > > > } > > > > > > > > > > > > > > > > where context is something like "top" or "error-info", etc. > > > > > > > > > > > > > > > > It is trivial to use groupings if the same set of nodes needs to be > > used > > > > in different contexts: > > > > > > > > > > > > > > > > > > > > yang-data error-info/name1 { > > > > > > > > container mydata; > > > > > > > > } > > > > > > > > > > > > > > > > Only the context named "top" is restricted to a resulting > > single-container > > > > > > > > and cannot have duplicate names. > > > > > > > > > > > > > > > > This is OK: > > > > > > > > > > > > > > > > x:yang-data error-info/my-error1 { > > > > > > > > leaf reason {} > > > > > > > > } > > > > > > > > > > > > > > > > > > > > x:yang-data error-info/my-error2 { > > > > > > > > leaf reason {} > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Could a fix for this be something along the lines of: > > > > - yang-data names must be unique amongst other top level data nodes > > > > within the module. > > > > - if yang-data extensions are used at the top level then their name > > must > > > > be used as a single top level container. > > > > - if a yang-data extension is used within another structure then the > > > > yang-data name is excluded, and the top level nodes defined in the > > > > yang-data definition are used .... > > > > > > > > > > > > Every tool that implements yang-data has to be able > > > > > > > > to interpret a yang-data statement exactly the same way. > > > > > > > > > > > > > > > > If you want to reinvent XSD substitutionGroup, then do it right. > > > > > > > > I'm not familiar with them. From a quick read, I don't see how they > > are > > > > related to the problem that we are trying to solve here. > > > > > > > > > > > > > > > > > > > > > > > > A substitutionGroup allows a point int the schema to be identified by > > name. > > > > > > > > Different elements can be defined that match this name, which then can > > be > > > > > > > > used (like a YANG choice) at the specified schema point. > > > > > > > > (e.g. error-info above is like a substitutionGroup) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > Rob > > > > > > > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > Rob > > > > > > > > > > > > > > > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > > > > > > > On 16/04/2018 15:36, Andy Bierman wrote: > > > > > > > > Hi, > > > > > > > > > > > > > > > > I am strongly opposed to this change because it breaks the rule in > > YANG 1..1 > > > > > > > > that there cannot be 2 sibling nodes defined in the same module > > namespace.. > > > > > > > > > > > > > > > > IMO since any yang-data nodes are ALLOWED to be used at the top-level, > > > > > > > > then these top-level nodes cannot have conflicting names. > > > > > > > > > > > > > > > > It is very important when parsing an instance document that the > > instance > > > > data > > > > > > > > can be associated with the correct schema. This is not possible if the > > > > > > > > same top-level node has multiple yang-data nodes defined. > > > > > > > > > > > > > > > > If one needs to define data that is not top-level, (1) use > > > > augment-yang-data > > > > > > > > or (2) use a different module. > > > > > > > > > > > > > > > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Apr 16, 2018 at 5:56 AM, Martin Bjorklund <mbj@tail-f.com> > > wrote: > > > > > > > > Hi, > > > > > > > > While preparing draft-ietf-netmod-yang-data-ext-02, it turned out that > > > > it is not clear what, if any, restrictions should be enforced for > > > > yang-data structures. Even among the authors we have different ideas > > > > for how this should work. > > > > > > > > Background: > > > > > > > > In 8040, the original yang-data extension had a restriction that said > > > > that a yang-data structure MUST have exactly one container, since it > > > > wouldn't be possible to have a yang-data structure in an XML instance > > > > document otherwise. > > > > > > > > Since people want to use yang-data structures in other places, this > > > > restriction was lifted in the new draft: > > > > > > > > There is no longer an assumption that a yang data structure can > > > > only be used as a top-level abstraction, instead of nested within > > > > some other data structure. > > > > > > > > > > > > With this in mind, here's a use case that I think we ought to support: > > > > > > > > rpc my-first-rpc { > > > > description > > > > "Bla bla... > > > > If an error occurs, <error-info> will contain an instance of > > > > the yang-data structure 'my-first-rpc-error-info'."; > > > > ... > > > > } > > > > > > > > yang-data my-first-rpc-error-info { > > > > leaf reason { ... } > > > > container user-info { ... } > > > > } > > > > > > > > rpc my-second-rpc { > > > > description > > > > "Bla bla... > > > > If an error occurs, <error-info> will contain an instance of > > > > the yang-data structure 'my-second-rpc-error-info'."; > > > > ... > > > > } > > > > > > > > yang-data my-second-rpc-error-info { > > > > leaf reason { ... } > > > > leaf important-url { ... } > > > > } > > > > > > > > (maybe in the future we could even have a YANG extension statement to > > > > formalize the description: > > > > > > > > rpc my-first-rpc { > > > > ... > > > > opx:error-info-structure my-first-rpc-error-info; > > > > } > > > > > > > > but this is not point now.) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I see no reason to reinvent the grouping-stmt. > > > > > > > > You could easily say opx:error-info-structure argument is a grouping > > name > > > > > > > > as it is a yang-data name. > > > > > > > > > > > > > > > > > > > > > > > > > > > > In the example above, note that the leaf "reason" is present in both > > > > structures. IMO this is not a problem, since these structures are > > > > used in different contexts. > > > > > > > > My point is that I think we should impose as few restrictions as > > > > possible to the yang-data extension. It should be up to the user of > > > > yang-data to ensure that the structure is defined in such a way so > > > > that it can be used properly. For example, a structure that is > > > > supposed to describe an XML instance document cannot define two leafs > > > > at the top level. > > > > > > > > If the WG agrees with what I wrote above, we need to change the > > > > augment-yang-data extension so that you would write for example: > > > > > > > > yx:augment-yang-data /ex:my-first-rpc-error-info/ex:user-info { > > > > ... > > > > } > > > > > > > > Comments? > > > > > > > > > > > > > > > > /martin > > > > > > > > _______________________________________________ > > > > netmod mailing list > > > > netmod@ietf.org > > > > https://www.ietf.org/mailman/listinfo/netmod > > > > <https://urldefense.proofpoint.com/v2/url?u=https- > > 3A__www.ietf.org_mailman_listinfo_netmod&d=DwMFaQ&c= > > HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r= > > 9zkP0xnJUvZGJ9EPoOH7Yhqn2gsBYaGTvjISlaJdcZo&m=q6I_ > > yKbXVoahv9h5I1wZiQMUeHLZ5XWuMohEYtypmzs&s=jECZMhypw9LtuxzuntkFNM- > > 8lm7xpztYwDDLOxCM_8k&e=> > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > > netmod mailing list > > > > > > > > netmod@ietf.org > > > > > > > > https://www.ietf.org/mailman/listinfo/netmod <https://urldefense. > > proofpoint.com/v2/url?u=https-3A__www.ietf.org_mailman_ > > listinfo_netmod&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r= > > 9zkP0xnJUvZGJ9EPoOH7Yhqn2gsBYaGTvjISlaJdcZo&m=q6I_ > > yKbXVoahv9h5I1wZiQMUeHLZ5XWuMohEYtypmzs&s=jECZMhypw9LtuxzuntkFNM- > > 8lm7xpztYwDDLOxCM_8k&e=> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Joe Clarke
- Re: [netmod] yang-data-ext issues Kent Watsen
- [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Joe Clarke
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- [netmod] Extensions vs new YANG versions [was Re:… Robert Wilton
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] Extensions vs new YANG versions [was… Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Ladislav Lhotka