Path: utzoo!mnetor!motto!ecijmm!eci386!jmm
From: jmm@eci386.UUCP
Newsgroups: news.software.b
Subject: Re: Forwarding Cancels For Unreceived Articles
Keywords: anecdotal, long
Message-ID: <1989Sep19.164120.26245@eci386.uucp>
Date: 19 Sep 89 16:41:20 GMT
References: <5200@looking.on.ca> <66812@uunet.UU.NET> <1989Sep7.151826.11816@i88.isc.com> <3919@hplabsz.HPL.HP.COM> <5553@videovax.tv.Tek.com> <11111@looking.on.ca>
Reply-To: jmm@eci386.UUCP (John Macdonald)
Organization: R. H. Lathwell Associates: Elegant Communications, Inc.
Lines: 33

In article <11111@looking.on.ca> brad@looking.on.ca (Brad Templeton) writes:
> [...]
>
>All I know is that I put out around 200 cancel messages per day.  Most
>of them should never leave this site, and only a few are intended to
>make it more than one or two sites downstream.   Supersedes would have
>been a lot easier but we all know why I couldn't use it.
>
>It will cause no harm to send them all out over the whole subnet, it will
>just waste disk space and money.
>-- 
>Brad Templeton, Looking Glass Software Ltd.  --  Waterloo, Ontario 519/884-7473

Most of the discussion about the "cancels should be propagated netwide" is
perfectly correct, yet Brad's case shows an important exception.

If a cancel is processed on the original system and can ensure that the
article has never left that system (and is not irretrievably batched to
leave the system), then it is safe to handle the cancel locally only.

After the article has left the original system, then the earlier arguments
that the cancel should be propagated netwide are appropriate.

The trick is determining whether an article has "left the system".  I make
no claims about whether such a determination can be accurately made with
any of the current news transport mechanisms (particularily for all possible
combinations of batched/unbatched ihave/sendme partial feeds, etc.), but I
expect that C-news provides enough flexibility for a knowlegable sysadmin to
extend it to make such determinations for his own specific configuration.
-- 
"Software and cathedrals are much the same -          | John Macdonald
first we build them, then we pray" (Sam Redwine)      |   jmm@eci386