Subject: Re: [netmod] extensions and conformance

From: Randy Presuhn <[email-masked]>
Date: Wed, 19 Aug 2015 17:45:21 -0700 (GMT-07:00)

Hi -

>From: Martin Bjorklund <[email-masked]>
>Sent: Aug 19, 2015 10:49 AM
>To: [email-masked]
>Cc: [email-masked]
>Subject: Re: [netmod] extensions and conformance
...
>> > Juergen suggested this replacement text, which I support.  Maybe it
>> > can be improved even more.
>> >
>> >        If a YANG parser does not support a particular extension, which
>> >        appears in a YANG module as an unknown-statement (see Section 13),
>> >        the entire unknown-statement MAY be ignored by the parser. Note
>> >        that even in this case the semantics associated with the extension
>> >        still apply (as if they were part of a description statement).
...
>No.  It means that if a server advertises module that uses some
>extension to define some behaviour, the server supports that
>behavior.  Just as we expect a server to support the text in
>description statements.

Sorry, but that interpretation is not supported by the 2119 definition
of MAY.

>For example, the nacm: extensions do not apply unless ietf-netconf-acm
>is advertised (and nacm is enabled).  I expect most extensions to work
>this way.  Another example is if we actually defined i2rs:ephemeral;
>this would have no effect unless the "i2rs" capability (whatever that
>is) is also advertised.
>
>The text also means that it is perfectly ok for a client to ignore the
>extension if it doesn't understand it.  For example, if the client has
>no idea what the ephemeral datastore it, it doesn't matter that a node
>is marked with i2rs:ephemeral true.

You are describing something stronger than a naked MAY.

You're describing an "if x MUST y".  If the conformance requirement
is truly simply MAY, then support is OPTIONAL even if the system
claims conformance.

Randy

---

From: Martin Bjorklund <[email-masked]>
Date: Thu, 20 Aug 2015 08:43:27 +0200 (CEST)

> Sorry, but that interpretation is not supported by the 2119 definition

Note that the original text says "if x then MAY y".  Juergen's text
says the same.  Maybe this should be rephrased...

/martin

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