Re: [netmod] yang-data-ext issues
Robert Wilton <rwilton@cisco.com> Mon, 16 April 2018 16:46 UTC
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To: Andy Bierman <andy@yumaworks.com>, Martin Bjorklund <mbj@tail-f.com>
Cc: NetMod WG <netmod@ietf.org>
References: <20180416.145617.1262098657698751846.mbj@tail-f.com> <CABCOCHQS5SdJhZrgoVug4Lux2WLCmieN26Kte_FEdzh9VB=riw@mail.gmail.com> <ef8e1caf-686e-1074-d094-6b6cd907a1a8@cisco.com> <CABCOCHRr=h=G43aJqwVRc+pcs-QV93_adHB4hDQckkVpacH8eA@mail.gmail.com>
From: Robert Wilton <rwilton@cisco.com>
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Date: Mon, 16 Apr 2018 17:46:34 +0100
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Subject: Re: [netmod] yang-data-ext issues
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On 16/04/2018 17:07, Andy Bierman wrote: > > > On Mon, Apr 16, 2018 at 8:44 AM, Robert Wilton <rwilton@cisco.com > <mailto: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. 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. Thanks, Rob > > > 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 >> <mailto: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 <mailto:netmod@ietf.org> >> https://www.ietf.org/mailman/listinfo/netmod >> <https://www.ietf.org/mailman/listinfo/netmod> >> >> >> >> >> _______________________________________________ >> netmod mailing list >> netmod@ietf.org <mailto:netmod@ietf.org> >> https://www.ietf.org/mailman/listinfo/netmod >> <https://www.ietf.org/mailman/listinfo/netmod> > >
- 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