From: Bruce Lilly (blilly@erols.com)
Date: Mon Mar 15 2004 - 20:08:44 CST
Charles Lindsey wrote:
> In <4054E853.6080200@erols.com> Bruce Lilly <blilly@erols.com> writes:
>
>
>>Charles Lindsey wrote:
>
>
>>>The more interesting point is whether to say anything about the case where
>>>a user follows up to two or more predecessors (as John Stanley frequently
>>>does in this thread). I posted a suggestion about this a few days back,
>>>but nobody commented (essentially, I suggested that all you wanted was
>>>that followups should occur later in the References header than any
>>>precursor).
>
>
>>The important thing is that the multiple message-ids of the multiple
>>immediate predecessors should be in the In-Reply-To field.
>
>
> The In-Reply-To header is not, and never has been, a part of Netnews.
Both RFC 850 and RFC 1036 use RFC 822 as a basis, and In-Reply-To
is defined in RFC 822; there is nothing in RFCs 850/1036 that
precludes use of In-Reply-To. In-Reply-To may be found in Usenet
articles (if you look, you will find it).
Except for the trivial case of a followup to multiple messages,
where each of those earlier messages has no predecessors, the only
efficient way to provide reliable indication that the message is in
fact a followup to multiple predecessors is via In-Reply-To or
something equivalent to it.
If one has only a bunch of message-ids, there is no way to determine
which articles corresponding to those message-ids are immediate
predecessors by examining the message with those message-ids in a
References field. If all of the messages corresponding to the
message-ids are available (not always the case) and if it is not
inefficient to retrieve the References fields from each of those
messages (possibly true if IMAP is used, maybe true if articles
are directly available, probably not true if access is via NNTP),
then it is possible to construct a dependency graph. However, even
if all of those conditions are met and after the graph is constructed,
it is still not possible to positively identify the messages being
directly referenced in all cases (one of the predecessors may itself
be a predecessor of another).
RFC 2822 section 3.6.4 details how In-Reply-To (and References) is
used when replying to multiple messages.