Re: [netmod] WHEN statement within mandatory objects doesn't ensure presence of the mandatory object

Robert Wilton <rwilton@cisco.com> Tue, 16 October 2018 13:41 UTC

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To: Michael Rehder <Michael.Rehder@Amdocs.com>, Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
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From: Robert Wilton <rwilton@cisco.com>
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Date: Tue, 16 Oct 2018 14:41:31 +0100
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Subject: Re: [netmod] WHEN statement within mandatory objects doesn't ensure presence of the mandatory object
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Hi Mike,


On 16/10/2018 14:26, Michael Rehder wrote:
> I've read rfc6110 and I didn't see any mention of "WHEN" on the mandatory status (section 9.1.1 Optional and Mandatory Nodes doesn't list it which seems a bit odd to me).
> The section on "WHEN" just mentions the xpath mapping, not anything about changing the mandatory status of the enclosing node.
>
> I still think that the YANG RFC wording of "conditional" needs to indicate if the node is mandatory status is affected or not.
> Note that rfc6060 "3.1 Mandatory Nodes" doesn't mention "WHEN" (it does mention presence).
By YANG RFC do you mean RFC 6020/7950?

Section 8.1 of RFC 7950 states the following constraints apply on valid 
data trees:

    o  There MUST be no nodes tagged with "when" present if the "when"
       condition evaluates to "false" in the data tree.

    o  The "mandatory" constraint is enforced for leafs and choices,
       unless the node or any of its ancestors has a "when" condition or
       "if-feature" expression that evaluates to "false".

    o  The "min-elements" and "max-elements" constraints are enforced for
       lists and leaf-lists, unless the node or any of its ancestors has
       a "when" condition or "if-feature" expression that evaluates to
       "false".

These rules indicate that "when" trumps "mandatory", "min-elements" and "max-elements".

Thanks,
Rob
  

>
> Thanks
> Mike
>> -----Original Message-----
>> From: Juergen Schoenwaelder [mailto:j.schoenwaelder@jacobs-university.de]
>> Sent: Saturday, October 13, 2018 5:20 PM
>> To: Michael Rehder <Michael.Rehder@Amdocs.com>
>> Cc: netmod@ietf.org
>> Subject: Re: [netmod] WHEN statement within mandatory objects doesn't
>> ensure presence of the mandatory object
>>
>> On Fri, Oct 12, 2018 at 04:08:48PM +0000, Michael Rehder wrote:
>>
>>> The mandatory statement in that case is ignored (I’ve pointed out the
>>> RNG and Schematron lack of enforcement).  WHEN trumps the mandatory
>>> status (via explicit mandatory or implicit mandatory via min-elements
>>> 1)
>> Has the RNG and Schematron been obtained following RFC 6110? If so, this may
>> be a problem with RFC 6110 but not with YANG itself. There are validators that
>> do not use RNG or Schematron.
>>
>> /js
>>
>> --
>> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
>> Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
>> Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>
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