Errors-to: owner-drums@CS.UTK.EDU
Date: Thu, 14 Sep 1995 17:39:12 +0200 (MET DST)
From: Jacob Palme <jpalme@dsv.su.se>
To: ietf-drums <drums@CS.UTK.EDU>
Subject: Re: Another header-munging example
Message-Id: <Pine.SUN.3.91.950914173829.23053E-100000@ester.dsv.su.se>
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Keith Moore writes:

> Personally, I see a real danger that we'll damage interoperability
> if we define more ways to do essentially the same thing (say, tell
> a user agent where to send replies), and some of the proposals for
> new headers do exactly that.  We need to encourage greater uniformity
> in user agent behavior, and the best way to do that is to encourage
> a more narrow interpretation of the existing 822 headers.

If existing 822 headers are interpreted in two different ways
by much existing software, then there is an obvious risk that
the outcome of the process you describe will be either:

(a) An ambiguous compromise to make everyone happy, but keeping
the two different interpretations and the trouble which is caused
by them.

(b) Recommending only one of the two, after which much existing
software maybe will not follow the new standard because they do
not like it.

In at least some cases, there is a better way:

(1) Standardize *two* new headers for the two old interpretations.

(2) Keep the old header, with its ambiguity, but recommend that
it should not be used and that if there is both the old and the
new header on the same message, only the new is valid.

If we do it that way, then no system will work worse than it did
before, and proponents of both alternatives can implement their
choice (or, better, both) and after five years or so, we can
abolish the old header altogether and the problem will disappear.

--- --- ---

An example with the old ambiguous header "Reply-To:".

Mail senders who want to redirect replies to the list will
implement two or three header lines:
Reply-To: list@domain
Wide-Reply-To: list@domain
Personal-Reply-To: mailbox@domain

Mail recipients who understand the new lines will ignore
the "Reply-To" and only follow the direction in the
either the "Wide-Reply-To" or the "Personal-Reply-To".

Mail recipients who do not understand new lines will
use the old-style "Reply-To" and be no worse than before.

Eric Thomas can have his Listserv add "Reply-To" and "Wide-Reply-To"
(but not "Personal-Reply-To") to mail resent to those list members
who prefer an interventionist mail expander.

---

Conclusion: Redefining the present ambiguity will either keep
the ambigiuity and the problem, or create a standard which will
not be adhered to. In both cases, problem for ever onwards.

Defining two new headers, and successively obsoleting the old
header, will allow a gradual migration to a world where the
problem does not occur.

------------------------------------------------------------------------
Jacob Palme <jpalme@dsv.su.se> (Stockholm University and KTH)
for more info see URL: http://www.dsv.su.se/~jpalme