LISTRIVIA (Duplicate postings)

Peter Murray-Rust peter at
Sat Dec 20 00:51:11 GMT 1997

At 14:24 19/12/97 -0800, Jon Bosak wrote:
[... in support of unnecessary bytecount on the list...]

It's something that comes partially out of the SGML culture. When I first
started posting to comp.text.sgml, I was quickly shown by Erik Naggum -
gently but very firmly - the appropriate way to use quoting. For those who
remember his time on c.t.s., I think Erik is one of the most precise people
I have "met" on the Internet.

There is another matter of style, which I was going to raise at an
appropriate time, but which Jon's contribution has catalysed me to mention.
On XML-SIG there is a very strict policy against duplicate postings.
Penalties (which of course are confidential) are Draconian.  I'll explain
the problem...

A duplicate posting occurs when someone (B) replies to the list and
simultaneously to the poster (A). If you do the arithmetic you will see
that the original poster (A) gets two copies of the message, one from the
list (L) and one from (B). Not quite identical because the headers are
different, so they *look* like different messages. It gets quite
disappointing for (A) to find that it's the same old letter again. Again,
if you do the sums you will see that (A) gets about twice as many bytes as
they really want. If you think deeply about the psychology, you'll see that
it often has a similar effect on (A) as unnecessary quoting has.

Now, if you don't *post* to the list, you won't be aware of this. BUT, if
you do, then you'll find that sometimes you get two copies with the same
content.  You'll also start to recognise the people who fall into category

Why do they do it? Not because (B) wants to upset (A), IMO. It works
something like this:

When (B) gets a message posted by (A) to the list, (B) will see two fields
in the header, something like this:

To: xml-dev at
From: A

[This is not very attractive markup, and will look much nicer when mailers
represent it as:

<TO>xml-dev at</TO>

but a surprisingly large number of people can, in fact, interpret the first
syntax without error. It is normally taken to mean that A sent a message to
xml-dev at, and that xml-dev at sent it on to all the

Now, it starts to get a bit complicated. Let's assume that B is a member of
XML-DEV, and wants to reply so that everyone can see what they (B) have
written. Most mailers have a "Reply" option, often on a menu, or by
pressing the "R" key. If you simply Reply to the message, it will go to
(A), because most mailers look in the "From" field and assume that you want
to send to the address represented by the content of the "From:" fields. So
the mailer would generate a reply something like:

To: A
From: B

and the message would go to (A), the original poster.

Rats! This isn't what B wanted. Of course they (B) want (A) to read the
message, but they also want everyone else on XML-DEV to read it. One way to
do it would be to type the words "xml-dev at" into the "To:" field,
like this:

To: xml-dev at
From: B

and, perhaps surprisingly, this actually works - i.e. it sends a message
from B to the XML-DEV list.

So, what's the problem? Well, typing "xml-dev at" is 16 characters
and it's very tedious to type this and check that it's right. So there's a
clever way round this. Many mailers have a "Reply to All" function. This
looks at everyone mentioned in the mail header and sends them all a copy of
the mail. So when (B) Replys in this fashion, their outgoing mail header
looks something like this:

To: xml-dev at, A
From: B

So everyone on XML-DEV and A gets a copy. This is just what B wants.
Everyone's happy. 

Unfortunately not. There's a very subtle point which lots of people quite
naturally miss. A gets sent a message. And everyone on XML-DEV gets a
message. But wait! A is a member of XML-DEV. The majordomo at
isn't clever enough to know that B has sent their own personal copy of the
mail to A. So, if you do the arithmetic, you'll se that A gets TWO copies
of the message. And, if you think very carefully, you'll see that they
aren't quite the same. One has a header saying that it has come from
XML-DEV, and the other that it has come from B. But the content of the two
messages is the same.

What can be done about it? Well, those of you who have followed so far will
see that deleting the string "A" from the To: field will solve the problem.
But this is often quite long - it might be something like:

"Peter Murray-Rust" <peter at>

which is now *45* characters - a lot of deleting. And easy to miss one out.
But there's a clever trick, which perhaps not everyone knows (and probably
works on most mailers).  It needs practice, but most people learn in time.

A. click the cursor just in front of the string you want to remove. You may
see a vertical bar, or block character.

B. Without taking your finger off the mouse, move it slowly to the right.
The background to the letters will go green! [It might be blue on some
machines, but don't worry.] When you've got to the end of the string (the
one you want to delete) take your finger *off* the mouse.  The background
will still be green!

C. Now - before you do anything else, find the "Delete" key. It's usually
got "Delete" written on it. Sometimes it says "Del", or sometimes "DEL".
Press it firmly, just once. The green string will disappear, *and* all the
letters in it.

D. *Now* you can press the "Send" button. If you work it out, your To:
field will be simply:

To: xml-dev at

just as if you'd typed it in, but so much less effort.

I realise this has been a long tutorial, and we've not even been able to
cover the Cc: field, or what to do without a mouse. But if you can master
this, you'll probably be able to manage the Cc: field [It stands for "Copy"
and when you "Reply to all" you'll reply to people in that field as well.
If it happens to be (A) you can use the same technique to delete the

So, let's see if we can get the duplicate postings down to zero :-) Then I
won't even have to mention things that might otherwise happen...


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