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Re: [core] Comments on draft-ietf-core-yang-cbor-00

Ladislav Lhotka <lhotka@nic.cz> Wed, 25 May 2016 05:36 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
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Date: Wed, 25 May 2016 07:36:12 +0200
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To: Carsten Bormann <cabo@tzi.org>
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Subject: Re: [core] Comments on draft-ietf-core-yang-cbor-00
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> On 24 May 2016, at 17:55, Carsten Bormann <cabo@tzi.org> wrote:
> 
> On 24 May 2016 at 17:09:01, Ladislav Lhotka (lhotka@nic.cz) wrote:
>> <foo member-type="2">42</foo> 
> That brings up a question:
> 
> Are there any rules about the evolution of unions?
> 
> Can a YANG implementation rely on the relative position of union members staying the same over the evolution of modules?

Sec. 11 in 6020bis says that a type cannot be updated if it changes its semantics, which seems to be the case here.

> 
> Can a YANG implementation rely on a specific position in a union for what used to be the only permissible type in a previous version of a module?

Alternatively, the annotation could specify the member type by name, e.g.

   <host member-type="ietf-inet-types:ipv6-address">...</host>

and in JSON

"host": "..."
"@host": { "member-type": "ietf-inet-types:ipv6-address" }

Lada


> 
> Grüße, Carsten

--
Ladislav Lhotka, CZ.NIC Labs
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