Re: [Nmh-workers] Format function to create wrapped header lines?

[Ken Hornstein]

>OK, though it really ought be used only to help find messages that
>might be part of the thread, not to define it.

I don't think anyone uses it as the complete, ultimate list of messages
in that thread.  I suspect most programs that utilitze it only care
about the immediate parent message.

>References should be like that section at the end of a paper in a conference
>or journal, where you list the identities of all the earlier papers that your
>paper refers to (substituting message for paper.)  That cannot simply be all
>of the References from each earlier paper (message) with a reference to the
>most recent one tacked on...

Well, how they SHOULD be used, I can't really say.  I can only go by the
standards documents.

>Using the References header is just fine - just don't start making assumptions
>about what it will (or should) contain that conflict with how the header
>should really be being used.

Well ....

It looks like References came from Usenet/Netnews; it's mentioned in
RFC 1036.  That RFC basically says, "To construct the References header,
tack on the parent message-id to the existing References header.  You're
allowed to truncate it, but keep as many entries as possible".

RFC 5536 (whoah, someone updated those RFCs in 2009?  I didn't think people
were still using Usenet then!) basically says, "See RFC 5322".

RFC 5322 says, §3.6.4:

   The "References:" field will contain the contents of the parent's
   "References:" field (if any) followed by the contents of the parent's
   "Message-ID:" field (if any).  If the parent message does not contain
   a "References:" field but does have an "In-Reply-To:" field
   containing a single message identifier, then the "References:" field
   will contain the contents of the parent's "In-Reply-To:" field
   followed by the contents of the parent's "Message-ID:" field (if
   any).  If the parent has none of the "References:", "In-Reply-To:",
   or "Message-ID:" fields, then the new message will have no
   "References:" field.

      Note: Some implementations parse the "References:" field to
      display the "thread of the discussion".  These implementations
      assume that each new message is a reply to a single parent and
      hence that they can walk backwards through the "References:" field
      to find the parent of each message listed there.  Therefore,
      trying to form a "References:" field for a reply that has multiple
      parents is discouraged; how to do so is not defined in this
      document.

_If_ MUAs are following the standards, then a References header should
contain a complete list of parent messages back to the origin message.
I suspect that all threading programs care about is the immediate parent,
though.  I recall Ralph had some reason he used References instead of
In-Reply-To, but I don't remember what it was.

--Ken