[ticker-dev] Replacement? Supersedes? Something else?

[Phil Cook]

On Monday 24 September 2001 20:09, Ted Phelps wrote:
> Because of these side-effects, I don't recommend that we use the
> `Supersedes' scheme.  They do, however, suggest another scheme which I
> quite like: we could merge the `Message-Id' and `Supersedes' fields.
> Thus, if Message B arrives which has a Message-Id that matches a
> message already received (Message A), then Message B replaces Message
> A.  Like the `Supersedes' scheme, this has the advantage/disadvantage
> that any message can be replaced, but without the unusual
> side-effects.

This certainly is an elegant approach (I think it did come up at the w/shop, 
but I can't recall the outcome).  Could it lead to problems with existing 
clients that assume Message-Ids are unique?  KTickertape and XTickertape (as 
far as I recall) wouldn't be too worried about this (though they would have 
to be modified to get the intended semantics right of course), but I don't 
know the internals of any other clients well enough to know if they'd have 
trouble with it or not.

I'm still concerned, however, by the potential for malicious use.  The idea 
of using this scheme for fixing typos seems neat at first, but I'm not 
convinced of its necessity, or even desirability.  Typos have become part of 
tickertape culture.  People expect and tolerate them, and they can even be 
sources of amusement (jokes based on sed will never get old!).  More 
importantly, however, I think the scheme is potentially confusing because it 
could seriously break the user's very simple mental model of tickertape 
interaction (temporal effects come to mind).  Furthermore, it is unclear 
exactly how non-scrolling clients should implement the scheme, whereas 
Replacement can be safely ignored by such clients.

Phil.
_____________________________________________________________________________
Phil Cook						 "No Neil, after you"
Ph.D. student at large						- Buzz Aldrin
School of Computer Science & Electrical Engineering
The University of Queensland, QLD, 4072, Australia