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From: pcolmer@acorn.co.uk (Philip Colmer)
Newsgroups: news.software.b
Subject: Thread following in newsgroups
Message-ID: <5871@acorn.co.uk>
Date: 15 Mar 91 11:04:02 GMT
Sender: pcolmer@acorn.co.uk
Distribution: news
Organization: Acorn Computers Ltd, Cambridge, England
Lines: 46

My apologies if this is not the right newsgroup for the following query. If
it isn't, perhaps someone could direct me at the right newsgroup.

For about 6 months now, we have been using a news reader which I wrote and I
am considering revisiting it to improve certain areas of its functionality.
One of those areas is the way it follows threads.

Thread following does not appear to be an easy thing to achieve. Consider
the following articles:

 (1) Subject: foo
 (2) Subject: Re: foo
 (3) Subject: Re: foo
     References: <1>
 (4) Subject: Re: foo
     References: <2>
 (5) Subject: Bar (was Re: foo)
     References: <3> <1>

This is not the most pathalogical example of the sort of situation news
readers have to cope with, but it should do.

Now, I suspect that the most logical order for reading these would be
1,2,4,3,5 or 1,3,5,2,4. When I started writing my news reader, the approach
I took was one of if the next article refers to the ORIGINAL article, then
display it. This is obviously flawed because there is absolutely no
guarantee that the original article will be referenced. So the rule got
changed to check for references to the last read article as well. This was
better, but it still wouldn't catch articles like (2).

So, the current approach is to display any article which either refers to
the last read article OR whose subject line contains the same subject as the
last read article. This certainly seems to catch all the articles in a
thread, but it also causes branches away due to articles like (5).

Finally, one of the requests I've had is to try and display the articles in
the "right" order. Due to the vagaries of the news system, it is often
possible for a reply to arrive at our site before the original article!

So, after all that, does anyone have any logic or techniques that could be
used in my news reader to make my thread following better?

--Philip Colmer

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Philip Colmer, OA Project Leader, Acorn Computers Ltd (pcolmer@acorn.co.uk)