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

[Michael Rehder <[e-mail]>]

Ok, so it is there in the RFC, just somewhat separated (in my view) from the definition of “when”.

I still am somewhat surprised by this implementation.
Far more often the I see a need to enforce the presence of a variant.

Thanks
Mike

From: Robert Wilton [mailto:[e-mail]]
Sent: Tuesday, October 16, 2018 9:42 AM
To: Michael Rehder <[e-mail]>; Juergen Schoenwaelder <[e-mail]>
Cc: [e-mail]
Subject: Re: [netmod] WHEN statement within mandatory objects doesn't ensure presence of the mandatory object


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:[e-mail]]

Sent: Saturday, October 13, 2018 5:20 PM

To: Michael Rehder <[e-mail]><mailto:[e-mail]>

Cc: [e-mail]<mailto:[e-mail]>

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

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