Randy Presuhn <[email protected]> wrote:
> Hi -
> 
> >From: Martin Bjorklund <[email protected]>
> >Sent: Aug 19, 2015 10:49 AM
> >To: [email protected]
> >Cc: [email protected]
> >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.

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


/martin


> >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
> 
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