Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!watmath!looking!brad
From: brad@looking.on.ca (Brad Templeton)
Newsgroups: news.software.b
Subject: How do articles get in the wrong order?
Message-ID: <10478@looking.on.ca>
Date: 10 Sep 89 17:35:52 GMT
References: <5200@looking.on.ca> <66812@uunet.UU.NET> <1989Sep7.151826.11816@i88.isc.com> <3919@hplabsz.HPL.HP.COM>
Reply-To: brad@looking.on.ca (Brad Templeton)
Organization: Looking Glass Software Ltd.
Lines: 53
Class: query

It might be useful to list the ways in which articles can get in the wrong
order.

There are three classes of such problems:

	a) Inews goofs up on your own machine
	b) They are transmitted to you in the wrong order from a machine
	   that got them in the right order
	c) The articles came by different routes resulting in the wrong order.

And a special case:
	d) The articles only *look* in the wrong order.  In fact, the first
	   article was superseded (or cancel/repost).

Here are some of my thoughts on different methods.  If we can list these out,
maybe we can make some news software that eliminates some or all of these.
In particular, maybe we can make a batcher/unbatcher to do part of the work.

A)
	The original comes in while expire's running.  The followup comes
	in after expire runs, but before articles queued for later processing
	get processed.  (Also applies to other things that spool articles for
	later processing)

		Solution:  Empty the queue ASAP.  If a new article comes in,
		empty anything in the queue first.

B)	This one's hard to figure.  Normally uucp and other transport mechs
	send stuff in the order they got it, unless their sequence numbers
	wrap around.  There might be problems caused by interrupted
	transmissions or people who move news at different priorities.

	Cross posting on a followup article that's not on the original can
	allow the followup to take a higher priority path, but this is rare.

C)	Again, for this to happen, we need something to go wrong.  The
	faster of your feeds has to lose the original, so that the followup
	gets there before the slow route sends the original.

	Because normally originals and followups have the same newsgroups
	line, and they will both move on any channel that moves one.

Problem C is the hardest to deal with.

So my questions:
	What other methods are there?
	Which is the most *common* cause of articles in the wrong order?

	Can the most common causes be fixed?


-- 
Brad Templeton, Looking Glass Software Ltd.  --  Waterloo, Ontario 519/884-7473