Re: [netmod] Adding a pre-existing leaf into a new 'choice' - NBC change?
Andy Bierman <andy@yumaworks.com> Thu, 22 November 2018 13:53 UTC
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From: Andy Bierman <andy@yumaworks.com>
Date: Thu, 22 Nov 2018 05:52:53 -0800
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To: Martin Bjorklund <mbj@tail-f.com>
Cc: Ladislav Lhotka <lhotka@nic.cz>, "Sterne, Jason (Nokia - CA)" <jason.sterne@nokia.com>, NetMod WG <netmod@ietf.org>
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Subject: Re: [netmod] Adding a pre-existing leaf into a new 'choice' - NBC change?
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On Thu, Nov 22, 2018 at 5:39 AM Martin Bjorklund <mbj@tail-f.com> wrote: > Hi, > > Ladislav Lhotka <lhotka@nic.cz> wrote: > > Andy Bierman <andy@yumaworks.com> writes: > > > > > On Mon, Nov 19, 2018 at 12:32 PM Sterne, Jason (Nokia - CA/Ottawa) < > > > jason.sterne@nokia.com> wrote: > > > > > >> Hi all, > > >> > > >> > > >> > > >> If we have a YANG model with a leaf: > > >> > > >> > > >> > > >> MODEL VERSION 1: > > >> > > >> container my-model { > > >> > > >> leaf a { type string; } > > >> > > >> } > > >> > > >> > > >> > > >> And then later we produce another version of the model where that > leaf is > > >> placed into a choice construct: > > >> > > >> > > >> > > >> MODEL VERSION 2: > > >> > > >> container my-model { > > >> > > >> choice some-choice { > > >> > > >> case x { > > >> > > >> leaf a { type string; } > > >> > > >> } > > >> > > >> } > > >> > > >> } > > >> > > >> > > >> > > >> Is that considered a non-backwards-compatible change? > > >> > > > > > > > > > yes -- even though the data node /my-model/x did not change, > > > the schema node /my-model/a changed to /my-model/some-choice/x/a. > > > Any leafref path pointing at this leaf will break. > > > > This is not correct. A leafref path is a special XPath, and as such > > includes only data nodes, i.e. NOT choice and case nodes. > > > > What does change are schema node identifier. This could be significant > > in an augment statement, but not ini this example because a leaf cannot > > be augmented anyway. > > > > I don't see anything else that could break, so Jason's change seems > > backward compatible to me. > > Since it does change the schema tree, this is not legal according to > 7950. So in that sense it is not backwards compatible. The rules in > 7950 protect both clients and other modules that import the module. > > This text is confusing wrt/ schema tree vs data tree: 9.9 <https://tools.ietf.org/html/rfc7950#section-9.9>. The leafref Built-In Type The leafref built-in type is restricted to the value space of some leaf or leaf-list node in the schema tree and optionally further restricted by corresponding instance nodes in the data tree. The "path" substatement (Section 9.9.2 <https://tools.ietf.org/html/rfc7950#section-9.9.2>) is used to identify the referred leaf or leaf-list node in the schema tree. The value space of the referring node is the value space of the referred node. > > /martin > > Andy > > > > > > Lada > > > > > > > > > > > Andy > > > > > > > > >> > > >> Does the answer depend on whether the choice contains other cases (or > > >> other cases that are the default case)? > > >> > > >> > > >> > > > > > > no > > > > > > > > >> MODEL VERSION 3: > > >> > > >> container my-model { > > >> > > >> choice some-choice { > > >> > > >> case x { > > >> > > >> leaf a { type string; } > > >> > > >> } > > >> > > >> case y { > > >> > > >> leaf b { type string; } > > >> > > >> } > > >> > > >> } > > >> > > >> } > > >> > > >> > > >> > > >> A client 'foo' using VERSION 1 would still be able to set & read back > leaf > > >> a in the same way as it always did. > > >> > > >> > > >> > > >> But if another client 'bar' (using VERSION 3) sets leaf 'b', then > leaf 'a' > > >> would disappear. That could be surprising to client 'foo' although > perhaps > > >> no more surprising than if another client simply deletes leaf 'a' > (using > > >> VERSION 1). > > >> > > >> > > >> > > >> Jason > > >> > > >> > > >> > > >> > > >> > > >> > > >> _______________________________________________ > > >> netmod mailing list > > >> netmod@ietf.org > > >> https://www.ietf.org/mailman/listinfo/netmod > > >> > > > _______________________________________________ > > > 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 > > >
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- [netmod] Adding a pre-existing leaf into a new 'c… Sterne, Jason (Nokia - CA/Ottawa)
- Re: [netmod] Adding a pre-existing leaf into a ne… Sterne, Jason (Nokia - CA/Ottawa)
- Re: [netmod] Adding a pre-existing leaf into a ne… Andy Bierman
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Sterne, Jason (Nokia - CA/Ottawa)
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Andy Bierman
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Sterne, Jason (Nokia - CA/Ottawa)
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Per Hedeland
- Re: [netmod] Adding a pre-existing leaf into a ne… Andy Bierman
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Robert Wilton
- Re: [netmod] Adding a pre-existing leaf into a ne… Martin Bjorklund
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Andy Bierman
- Re: [netmod] Adding a pre-existing leaf into a ne… Juergen Schoenwaelder
- Re: [netmod] Adding a pre-existing leaf into a ne… Andy Bierman
- Re: [netmod] Adding a pre-existing leaf into a ne… Ladislav Lhotka