Newsgroups: news.software.b
Path: utzoo!utstat!geoff
From: geoff@utstat.uucp (Geoff Collyer)
Subject: Re: cancel propagation (was Re: Supersedes problems with rapid-fire articles)
Message-ID: <1989Sep1.004629.17171@utstat.uucp>
Organization: Statistics, U. of Toronto
References: <5200@looking.on.ca> <536@logicon.arpa> <3246@deimos.cis.ksu.edu> <1989Aug30.174430.20687@anise.acc.com> <1989Aug31.034105.2177@utstat.uucp> <6233@looking.on.ca>
Date: Fri, 1 Sep 89 00:46:29 GMT

I don't believe one can assume, in general, that a site will get an
article and its cancel from the same neighbour, nor even assume that
they will travel the same routes.  Remember that notions of "upstream"
and "downstream" are fuzzy and don't even always apply to leaf sites.
Thus it is possible for a cancel to arrive before its target.  Throwing
away cancels (due to absence of its target) will tend to cause some
sites to never see a cancel even though they will see the target.
-- 
Geoff Collyer		utzoo!utstat!geoff, geoff@utstat.toronto.edu