Re: Proposed IESG Statement on the use of the “Updates” header

[Benjamin Kaduk <[e-mail]>]

On Fri, Sep 14, 2018 at 08:59:53AM +1200, Brian E Carpenter wrote:
> Hi Ben,
> 
> On 2018-09-14 01:34, Benjamin Kaduk wrote:
> > On Wed, Sep 12, 2018 at 08:56:23AM +1200, Brian E Carpenter wrote:
> >> On 2018-09-12 06:08, Robert Sparks wrote:
> >>> I can live with this statement, but I don't like it.
> >>>
> >>> I'm in the camp that prefers the more specific "This changes the code 
> >>> you need to write" camp - I would prefer Update be restricted to the 
> >>> cases where you are changing the protocol defined in the updated 
> >>> document in an essential way. 
> >>
> >> The IAB already opined indirectly on this topic.
> >> https://tools.ietf.org/html/rfc6709#page-5 says:
> >>
> >>>>>    Extension designers should examine their design for the following
> >>>>>    issues:
> >>>>>
> >>>>>    1.  Modifications or extensions to the underlying protocol.  An
> >>>>>        extension document should be considered to update the underlying
> >>>>>        protocol specification if an implementation of the underlying
> >>>>>        protocol would need to be updated to accommodate the extension.
> >>>>>        This should not be necessary if the underlying protocol was
> >>>>>        designed with a modular interface.
> >>
> >> (followed by more detailed discussion).
> >>
> >> I'm not sure the IESG text is 100% compatible with this.
> > 
> > I believe it was intended to be, and I'm not sure what incompatibility you
> > are seeing; could you say more?
> 
> There's a subtlety in this phrase:
>   "would need to be updated to accommodate the extension."
> Even though I'm a co-author of RFC6709, I'm not 100% sure what this means.
> I think it means "if an implementor adds the extension to the code, she must
> also modify the base code". The IAB text seems to be saying that if you add
> a feature that does not *require* a change to the existing code, it's
> not an update. I'm not sure I even agree with that, and I don't think
> the IESG text does either. (If it does, we need a new tag "Extends:".)

Ah, I see what you mean -- thanks.  Our situation seems to be similar to
the distinction between the converse and contrapositive in logic, though --
just because an Updates header is not necessary for this reason, does not
a priori prevent an Updates header from being used for some other reason.

-Ben