To: Jamie Zawinski <jwz@jwz.org>
Subject: message threading

Hi,

I'm implementing message threading, and have been referencing both
your document <https://www.jwz.org/doc/threading.html> and RFC 5256.
I'm not sure whether you're interested in updating a document that's
more than 25 years old, but if you are: I hope you find the following
feedback valuable.

You write that the algorithm in RFC 5256 is merely a "restating" of
your algorithm, but I noticed 3 (minor) differences:
   
1. In your step 1.C, the RFC says to check whether this would create a
   loop, and if it would to skip creating the link; your version only
   says to perform this check in step 1.B.
   
2. The RFC says to sort the messages by date between your steps 4 and
   5; that is: when grouping by subject, containers in the root set
   should be processed in date-order (you do not specify an order),
   and that if container in the root set is empty then the subject
   should be taken from the earliest-date child (you say to use an
   arbitrary child).

3. The RFC precisely states how to trim a subject down to a "base
   subject," rather than simply saying "Strip ``Re:'', ``RE:'',
   ``RE[5]:'', ``Re: Re[4]: Re:'' and so on."

Additionally, there are two minor points on which I found their
version to be clearer:

1. The RFC specifies how to handle messages without a Message-Id or
   with a duplicate Message-Id (on page 9), as well as how to
   normalize a Message-Id (by referring to RFC 2822).  This is perhaps
   out-of-scope of your algorithm document, but I feel that it would
   be worth mentioning in your background or definitions section.

2. In your step 1.B, I did not understand what "If they are already
   linked, don't change the existing links" meant until I read the
   RFC, which words it as "If a message already has a parent, don't
   change the existing link."  It was unclear to me what "they" was
   referring to in your version.

-- 
Happy hacking,
~ Luke T. Shumaker