> -----Original Message----- > From: Ladislav Lhotka <lho...@nic.cz> > Sent: 26 June 2019 08:01 > To: Rob Wilton (rwilton) <rwil...@cisco.com>; netmod@ietf.org > Subject: Re: [netmod] ?= ?==?utf-8?q? mandatory choice with non-presence > container cas > > On Tue, 2019-06-25 at 13:49 +0000, Rob Wilton (rwilton) wrote: > > > -----Original Message----- > > > From: netmod <netmod-boun...@ietf.org> On Behalf Of Ladislav Lhotka > > > Sent: 25 June 2019 14:14 > > > To: netmod@ietf.org > > > Subject: Re: [netmod] ?= ?==?utf-8?q? mandatory choice with > > > non-presence container cas > > > > > > On Tue, 2019-06-25 at 13:59 +0200, Martin Bjorklund wrote: > > > > Michal Vaško <mva...@cesnet.cz> wrote: > > > > > Hi Rob, > > > > > actually, I have used model with the container TOP just for > > > > > simplification, I have encountered the issue while implementing > > > > > ietf-ssh-server model from its current draft. I have created the > > > > > container "users" [1] without any "user" list instances. Now, > > > > > you may argue that this is still not a valid use-case because > > > > > there are no users but I only tried to satisfy the condition. > > > > > > > > Yes, I think that this list (user) should have a "min-elements 1". > > > > I think that matches the i ntent. > > > > > > Interestingly, the "users" container actually becomes a P-container: > > > its presence indicates that the corresponding case is selected. > > > > I don't think that this makes it a P-container. > > Not formally, according to the current rules, but effectively "the > container itself carries some meaning" (sec. 7.5.1).
In a data tree, I think that the only meaning that an NP-container conveys is the existence of a descendent leaf, leaf-list, p-container, anydata, or anyxml data node. > > > > > > > > > It might make > > > sense for an admin to select this case even before any users are > > > configured. > > > > Sure, the "users" container could have been marked as having presence > > in the YANG model. > > > > > > > This example also exposes the drawback of the XML representation - > > > it cannot distinguish between an empty list and nothing. In JSON, > > > the problems of this thread could potentially be circumvented by > > > configuring > > > > > > "users" : { > > > "user" : [ > > > ] > > > } > > > > I don't think that an empty list "exists" in a configuration > > datastore, i.e. I > > I am not sure about this, it possibly depends on an implementation. Perhaps, but I argue that this is probably the only robust interpretation, particularly given that XML cannot represent a list that exists with no entries. Thanks, Rob > > Lada > > > don't think that it should impart any meaning, in that regard is seems > > somewhat like an NP-container. > > > > > Thanks, > > Rob > > > > > > > Lada > > > > > > > /martin > > > > > > > > > > > > > > > > > There are some users > > > > > on the system but they are generated into the configuration > > > > > on-demand when operational data is requested. > > > > > > > > > > Regards, > > > > > Michal > > > > > > > > > > [1] > > > > > https://tools.ietf.org/html/draft-ietf-netconf-ssh-client-server > > > > > -14# > > > > > page-22 > > > > > > > > > > On Tuesday, June 25, 2019 11:08 CEST, "Rob Wilton (rwilton)" > > > > > <rwil...@cisco.com> wrote: > > > > > > > > > > > Hi Michal, > > > > > > > > > > > > It is not the printing of the data that makes it valid/invalid. > > > > > > > > > > > > I don't think that your input data was ever valid, because > > > > > > "container C" doesn't satisfy the mandatory statement because > > > > > > it isn't a real data node in the tree - it is instantiated > > > > > > when required and may be deleted when it is no longer required. > > > > > > > > > > > > I.e. your model has been designed such that it can never be > > > satisfied. > > > > > > > > > > > > If your model was instead: > > > > > > > > > > > > container TOP { > > > > > > leaf L { > > > > > > type empty; > > > > > > } > > > > > > choice A { > > > > > > mandatory true; > > > > > > container C { > > > > > > leaf L2 { > > > > > > type empty; > > > > > > } > > > > > > } > > > > > > } > > > > > > } > > > > > > > > > > > > > > > > > > Then this data is valid: > > > > > > > > > > > > <TOP> > > > > > > <L/> > > > > > > <C> > > > > > > <L2/> > > > > > > </C> > > > > > > </TOP> > > > > > > > > > > > > > > > > > > But this data is not: > > > > > > > > > > > > <TOP> > > > > > > <L/> > > > > > > </TOP> > > > > > > > > > > > > > > > > > > Nor is this, which is directly equivalent to the one above, > > > > > > because the <C/> container doesn't really exist if it doesn't > > > > > > have a child node present. > > > > > > > > > > > > <TOP> > > > > > > <L/> > > > > > > <C/> > > > > > > </TOP> > > > > > > > > > > > > Thanks, > > > > > > Rob > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > > > > From: Michal Vaško <mva...@cesnet.cz> > > > > > > > Sent: 24 June 2019 18:15 > > > > > > > To: Andy Bierman <a...@yumaworks.com> > > > > > > > Cc: Rob Wilton (rwilton) <rwil...@cisco.com>; netmod > > > > > > > <netmod@ietf.org> > > > > > > > Subject: Re: [netmod] ?= mandatory choice with non-presence > > > > > > > container cas > > > > > > > > > > > > > > Hi Andy, > > > > > > > > > > > > > > On Monday, June 24, 2019 19:11 CEST, Andy Bierman > > > > > > > <a...@yumaworks.com> > > > > > > > wrote: > > > > > > > > > > > > > > > On Mon, Jun 24, 2019 at 10:01 AM Michal Vaško > > > > > > > > <mva...@cesnet.cz> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > Hi Rob, > > > > > > > > > I think there is a problem in the RFC because using only > > > > > > > > > allowed steps I got invalid data from initially valid > data. > > > > > > > > > That cannot be > > > > > > > correct. > > > > > > > > No. See sec. 7.5.7 > > > > > > > > > > > > > > > > If a non-presence container does not have any child > > > > > > > > nodes, > > > the > > > > > > > > container may or may not be present in the XML encoding. > > > > > > > > > > > > > > > > > > > > > > > > Just because your retrieval does not contain the > > > > > > > > NP-container, that does not mean the NP-container was not > > > > > > > > present in the server for the mandatory-stmt validation. > > > > > > > > > > > > > > I agree, but these valid data were correctly printed into > > > > > > > invalid data. I do not think printing is allowed to change > > > > > > > the validity of data. > > > > > > > > > > > > > > Michal > > > > > > > > > > > > > > > Regards, > > > > > > > > > Michal > > > > > > > > > > > > > > > > > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > > > > > > > > On Monday, June 24, 2019 18:52 CEST, "Rob Wilton > (rwilton)" > > > > > > > > > < rwil...@cisco.com> wrote: > > > > > > > > > > > > > > > > > > > Hi Michal, > > > > > > > > > > > > > > > > > > > > My thoughts: > > > > > > > > > > > > > > > > > > > > According to 7.5.1: > > > > > > > > > > > > > > > > > > > > In the first style, the container has no meaning of > > > > > > > > > > its own, > > > > > > > existing > > > > > > > > > > only to contain child nodes. In particular, the > > > > > > > > > > presence of the > > > > > > > > > > container node with no child nodes is semantically > > > > > > > > > > equivalent to > > > > > > > the > > > > > > > > > > absence of the container node. YANG calls this > > > > > > > > > > style a > > > > > > > > > > "non- > > > > > > > presence > > > > > > > > > > container". This is the default style. > > > > > > > > > > > > > > > > > > > > Hence your request (because the NP container does not > > > > > > > > > > have any > > > > > > > > > > children) > > > > > > > > > is equivalent to: > > > > > > > > > > <TOP> > > > > > > > > > > <L/> > > > > > > > > > > </TOP> > > > > > > > > > > > > > > > > > > > > which fails the "mandatory" check. > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Rob > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > > > > > > > > From: netmod <netmod-boun...@ietf.org> On Behalf Of > > > > > > > > > > > Michal Vaško > > > > > > > > > > > Sent: 24 June 2019 17:39 > > > > > > > > > > > To: netmod <netmod@ietf.org> > > > > > > > > > > > Subject: [netmod] mandatory choice with non-presence > > > > > > > > > > > container case > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > I have encountered a situation that I think is not > > > > > > > > > > > covered by RFC > > > > > > > > > 7950. My > > > > > > > > > > > specific use-case was as follows. > > > > > > > > > > > > > > > > > > > > > > model: > > > > > > > > > > > > > > > > > > > > > > container TOP { > > > > > > > > > > > leaf L { > > > > > > > > > > > type empty; > > > > > > > > > > > } > > > > > > > > > > > choice A { > > > > > > > > > > > mandatory true; > > > > > > > > > > > container C; > > > > > > > > > > > } > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > data: > > > > > > > > > > > > > > > > > > > > > > <TOP> > > > > > > > > > > > <L/> > > > > > > > > > > > <C/> > > > > > > > > > > > </TOP> > > > > > > > > > > > > > > > > > > > > > > Parsing was successful, but printing these data back > > > > > > > > > > > to XML > > > > > > > produced: > > > > > > > > > > > <TOP> > > > > > > > > > > > <L/> > > > > > > > > > > > </TOP> > > > > > > > > > > > > > > > > > > > > > > and parsing this correctly failed with missing > > > > > > > > > > > mandatory > > > choice. > > > > > > > > > According > > > > > > > > > > > to section 7.5.7 [1], I think the C container could > > > > > > > > > > > be omitted but the whole situation does not seem > correct. > > > > > > > > > > > Thank you for any > > > > > > > input. > > > > > > > > > > > Regards, > > > > > > > > > > > Michal > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > > > > > > https://tools.ietf.org/html/rfc7950#section-7.5.7 > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > 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 > -- > Ladislav Lhotka > Head, CZ.NIC Labs > PGP Key ID: 0xB8F92B08A9F76C67 _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod