Re: [netmod] Yang 1.1 change: Allow type "empty" in a key.

> On 15 Feb 2017, at 11:16, Jernej Tuljak <jernej.tuljak@mg-soft.si> wrote:
> 
> Plus, "empty keys" were aready allowed in YANG 1.

Well, keys with "empty" type were not allowed. What you are saying is that the same (dubious) effect can be achieved in other ways that were permitted in YANG 1. Note also that while if in XML encoding an empty leaf and a leaf containing string of length 0 look the same, in JSON encoding they are different:

"first": [null]

versus

"first": ""

>  
> module empty-key {
>   namespace "org:example:empty-key";
>   prefix "ek";
>  
>   container stuff {
>     list item {
>       key "first second";
>       leaf first {
>         type string {
>           length 0;
>         }
>       }
>       leaf second {
>         type string {
>           pattern '.{0}';
>         }
>       }
>     }
>   }
> }
>  
> Therefore this change removed a redundant (perhaps even broken) rule.

Agreed.

Lada

>  
> https://www.ietf.org/mail-archive/web/netmod/current/msg16763.html
> Jernej
>  
> From: netmod [mailto:netmod-bounces@ietf.org] On Behalf Of Alex Campbell
> Sent: Tuesday, February 14, 2017 9:59 PM
> To: Martin Ciglan -X (mciglan - PANTHEON TECHNOLOGIES at Cisco) <mciglan@cisco.com>
> Cc: Igor Foltin -X (ifoltin - PANTHEON TECHNOLOGIES at Cisco) <ifoltin@cisco.com>; netmod@ietf.org
> Subject: Re: [netmod] Yang 1.1 change: Allow type "empty" in a key.
>  
> Hi,
>  
> It means exactly what the summary says. In YANG 1.0 (RFC 6020) we have:
>    A leaf that is part of the key can be of any built-in or derived
>    type, except it MUST NOT be the built-in type "empty".
> and in YANG 1.1 (RFC 7950) we have:
>    A leaf that is part of the key can be of any built-in or
>    derived type.
> 
> In YANG 1.1, leaves of type "empty" are not disallowed from being keys.
> 
> Note that since leaves of type "empty" only convey information through their presence or absence, and since
> key leaves must always be present, key leaves of type "empty" convey no useful information.
>  
> Alex
>  
>  
> From: netmod <netmod-bounces@ietf.org> on behalf of Martin Ciglan -X (mciglan - PANTHEON TECHNOLOGIES at Cisco) <mciglan@cisco.com>
> Sent: Wednesday, 15 February 2017 2:48 a.m.
> To: netmod@ietf.org
> Cc: Igor Foltin -X (ifoltin - PANTHEON TECHNOLOGIES at Cisco)
> Subject: [netmod] Yang 1.1 change: Allow type "empty" in a key.
>  
> Hi all
>  
> Yang 1.1 change:  Allow type "empty" in a key.
> 
> What is the meaning of this change? We're interested from implementation point of view.
>  
>   Thanks
>  
>        Martin
> 
> _______________________________________________
> netmod mailing list
> netmod@ietf.org
> https://www.ietf.org/mailman/listinfo/netmod

--
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67