strathspey@strathspey.org:53366

Anselm Lingnau

Re: New threads please...

Aug. 11, 2008, 4:34 p.m. (Message 53366, in reply to message 53347)

xxxxxxxxxx@xxxxxxxxxx.xxx schrieb:

> This is the first time I have heard of threads being anything but
> meesages with a common subject line.

As Steve Johnson mentioned, the subject line has nothing to do 
with »threading« (although there are mail programs around that will take the 
easy shortcut of sorting messages according to subject line and will call 
that »threading«).

If done correctly, threading is performed according to the »Message-ID« 
and »In-Reply-To« (or »References«) headers. Every message is supposed to 
contain a unique »Message-ID« header that exists only once in the history of 
the world. For example, in the header of Martin's message I'm replying to 
there is a line saying

  Message-ID: <xxxxxxx.xxxxxxxxxxxxx.xxxxxxxx.xxxx@xxxxx>

If a message is a reply to another message, this message is then supposed to 
contain

  In-Reply-To: <xxxxxxx.xxxxxxxxxxxxx.xxxxxxxx.xxxx@xxxxx>

or

  References: <xxxxxxx.xxxxxxxxxxxxx.xxxxxxxx.xxxx@xxxxx>

A well-written mail reader can use these lines to construct a tree reflecting 
the flow of answers without actually looking at the subject lines. (The 
difference between »In-Reply-To« and »References« is that »References« can 
actually list a (technically) arbitrary number of preceding messages, i.e., 
follow the »branch« this message is the tip of possibly all the way up to its 
root -- the first message posted in the thread. This makes it easy to 
construct the tree even in the face of missing messages.) This is 
incidentally what the Strathspey Archive does when collecting messages into 
threads.

In practice, the problem is that the authors of many mail readers do not 
bother to get the »Message-ID« and »In-Reply-To«/»References« headers right, 
so header-based threading doesn't always work, and one does have to resort to 
looking at subject and date lines to figure out what belongs where. What the 
Strathspey Archive *really* does is use a method called the »Jamie Zawinski 
algorithm«, which does exactly that. We do have a slight advantage in that 
the order that my server processes incoming messages in imposes a strict 
ordering on the messages in the Archive, so every answer to a message must 
have been processed later than the message itself -- unlike the general case 
where questions and answers can cross each other all over the place. Hence 
the thread reconstruction in the Archive does work quite well (I'm happy to 
say); most glitches are due to terminally dumb client programs that won't put 
the headers in that they should.

>  None of the e-mail readers I have used sort the messages except by
> date (or subject or sender, depending on my own choice).    Which means
> that changing a subject line is, as far as I can tell the same thing as
> starting a new thread, the "was : " convention  being a possible way of
> connecting up with what had gone before.

That may be the case for you but, as I said, with properly-written software, 
subject lines are only looked at as a last resort.

Right, everybody, nutshell summary:

  - Please don't start an unrelated topic by replying to a message that is
    part of an existing thread. Even if you change the subject line it is
    going to mess up the archive. And »xxxxxxxxxx@xxxxxxxxxx.xxx« really
    ought to be reasonably easy to remember (if not to type, but that's what
    your address book is for). If you have a really good mail program it
    should offer a »post to mailing list« function that will start a new
    thread given an existing message from a mailing list.

  - Please keep the subject line reasonably close to what is actually being
    discussed. The policy to do this is like so: Consider the subject line:

      Subject: Re: Words for "Donald Where's Your Troosers"

    (thank you, Malcolm). Suppose that the discussion has, after a few dozen
    messages, drifted over to the perennial topic on which shoulder one should
    take in Mairi's Wedding. The way to adjust the subject line is to put

      Subject: Shoulder in Mairi's Wedding (was: Words for "Donald Where's
          Your Troosers")

    (line broken -- in the approved fashion) for readability. That is, you get
    rid of any »Re:«'s in front of the actual subject text and put that in
    parentheses with an added »was: « in front.

Incidentally, it is supposed to be »Re:« (not »RE:« or foreign abominations 
such as »AW:«) and there should be only one of those in a subject line. 
Hence, subject lines like

    Subject: RE: Re: AW: Re: Shoulder in Mairi's Wedding

are an indication of terminally brain-damaged client software.

Anyway, I have to go up to University Hall for my big shopping spree, so this 
concludes today's lesson on e-mail arcana and etiquette.

Anselm

PS. I swear that the quote below was randomly selected.
-- 
Anselm Lingnau, Friedberg, Germany ..................... xxxxxx@xxxxxxxxxx.xxx
There are no significant bugs in our released software that any significant
number of users want fixed.                                      -- Bill Gates