Folks,
It seems to me that three things are emerging on this thread.
(1) The original proposal and problem to be solved, at least as
most of us understood it, was to allow a sender to send some
sort of notification that would cause all copies of a message to
be automagically destroyed. We appear to have unanimity that
problem is unsolvable, at least in the general case and/or in
the absence of universal trust.
(2) We have considerable experience (in both email and netnew)
with putting out messages with expiry dates as information for
the recipient (whether expected to be acted on automatically or
not). While there are important exceptions, they have never
been as useful as was apparently assumed when they were
adopted... to the point that the IANA registry entries for the
relevant email header fields identify them as obsolete. We have
less experience with the originator of an already-sent message
as expired or obsolete, but no evidence has been offered so far
that such a facility would be appreciably more useful than the
"Expires:" header field.
(3) We have now reached the stage in which people seem to be
discussing alternate problems that can be solved. That isn't
very hard, but those alternate problems are not the original one
and little or no case is being made that the new problems are
worth solving or that solutions would be useful, even if they
are feasible.
It seems to me that, if people believe there is a problem worth
solving and if they think they have a feasible solution, we need
to see an I-D that explains both, rather than continuing to
circle around an ever-expanding collection of possible issues on
the IETF list in the absence of such a draft.
john