Sandman
In article <9rfol99hm6vquhjuuk14qgmql8c4h3s9o9@4ax.com>, Eric Stevens wrote:

RFC 5537, section 3.4.4

3.4.4. Construction of the References Header Field

The following procedure is to be used whenever some previous article (the "parent") is to be referred to in the References header field of a new article, whether because the new article is a followup and the parent is its precursor or for some other reason.

The content of the new article's References header field MUST be formed from the content of the parent's References header field if present, followed by the content of the Message-ID header field of the parent. If the parent had a References header, FWS as defined in [RFC5536] MUST be added between its content and the Message-ID header field content.

Ready to admit you were wrong, yet?

Eric Stevens
Your juvenile crowing is premature. The text you have quoted has been standard in RFCs going back for yoncks. What you have missed the first paragraph of 3.4.3

Sandman
That section is about followups, not the references header.

Eric Stevens
"A followup is an article that contains a response to the contents of an earlier article, its precursor. In addition to its normal duties, a posting agent preparing a followup is also subject to the following requirements. Wherever in the following it is stated that, by default, a header field is said to be inherited from one of those header fields in the precursor, it means that its initial content is to be a copy of the content of that precursor header field (with changes in folding permitted). However, posters MAY then override that default before posting."

Sandman
YOu snipped to early - this section states the rules for the Followup-To and the Newsgroups header, and says nothing about threading.

Eric Stevens
... so it is not mandatory that "The following procedure is to be used ... " with no exceptions.

Sandman
Incorrect.

Eric Stevens
More importantly these rules deal with follow ups. They say nothing about changes in subject lines.

Sandman
I.e. they determine the relation between posts (what we call a thread) which you now know has nothing to do with the subject line.

Eric Stevens
In fact I am aware of no rules, RFCs etc which deal with the treatment of threads when the subject line is changed.

Sandman
No, since there are no such rules, ...

... because changing the subject line doesn't warrant the news client to do anything. Threading is done via the References header, the subject line is irrelevant.

To be clear here - the References header is program-internal, the Subject line is discussion-related. It's all about the user-submitted content.

When you reply to a post, you can't change the references header, but you can change the subject line at your discretion. THis means that your post will be a part of the ongoing thread regardless of what subject line you type.

Eric Stevens
"THREAD A message and the replies to it for a discussion thread. All Usenet newsgroup messages that are not replies to other messages are new threads. A thread is the most common way to distinct particular messages from a post to track the community responses to the topic. A thread is an array of multiple posts on the same subject matter of the original posts. A thread is commonly distinguished by the RE: subject name in order to filter the messages that correspond to the original message that was posted on a particular newsgroup, or an array of Usenet newsgroups that handle the same subject matters in a variety of deviations. "

Sandman
This is incorrect. A thread is not "usually" determined by the subject line.

Eric Stevens
I would not regard this as a final authority but note that it says "A thread is an array of multiple posts on the same subject matter of the original posts" i.e. change the subject matter and you have a new thread.

Sandman
You have to realize, Eric, that "subject matter" (i.e. not the subject *header*) changes ALL THE TIME in threads. Those are referred to as "subthreads". I.e. they all belong to the same thread, but some parts of the hierarchy of posts have changed along the way as far as "subject matter" is concerned. Sometimes, as the "subject matter" is changed, some one might also change the subject header, this does NOT create a new thread.

Eric Stevens
This makes sense. 2.1.4 'Subject' of RFC 1036 states:

"The "Subject" line (formerly "Title") tells what the message is about. It should be suggestive enough of the contents of the message to enable a reader to make a decision whether to read the message based on the subject alone. ...... "

Sandman
Correct, which is why it's a great service to change the subject line to reflect the current subject of the ongoing thread. Again, new subject line for new discussion topic, but same old thread.

Eric Stevens
Any sensible news reader will sort messages by subject and if there is a change of subject it will place that message and it's follow-ups in a group all together.

Sandman
No, that would be a non-standard and incorrect way to handle threading.

Eric Stevens
As far as the reader is concerned it is a new thread.

Sandman
Incorrect. Well, if your news reader treats threading in a non-standard fashion, I have no problem seeing how you would THINK it's a new thread, but that doesn't make it a new thread.