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Subject: Example Digest Format
From: James M Galvin <galvin @ acm . org>
Date: Wed, 11 Apr 2001 10:25:52 -0400 (EDT)
To: list-managers @ greatcircle . com

Setting aside the discussion of whether digests are "good, bad, or
ugly", I am very interested in whether or not there is any consensus as
to what is an ideal format for a digest given that it will exist.

I want to use multipart/digest.  Here is what I have understood from the
discussion thus far.

    From: (see point 1 below)
    To: SUBMISSION_ADDRESS_FOR_DIGEST
    Subject: Digest #??
    Content-type: multipart/digest; boundary="line1"

    --line1

    Subject: Table of Contents (see point 2 below)

    LIST_OF_SUBJECTS (see point 3 below)

    --line1

    HEADERS_OF_DIGEST_MESSAGE #1 (see point 4 below)

    BODY_OF_DIGEST_MESSAGE #1

    --line1

    HEADERS_OF_DIGEST_MESSAGE #2

    BODY_OF_DIGEST_MESSAGE #2

    --line1--

Point 1:

    In my digests I set the From: message header to be the errors
    address for the list, making the default assumption that only error
    messages are "returned or replied" and choosing to filter out
    messages intended for the list.  My statistics are excellent in this
    regard.  It's also been suggested you can make it the digest
    submission address and instead filter out messages that do not
    belong on the list.  With the right filter either setting should be
    equally good.

Point 2:

    I incorrectly made the point that an embedded message/rfc822 needs
    to have a From:, Subject:, and Date:.  I checked again, carefully,
    and that is not what rfc2046 says.  It very carefully says that an
    outermost message/rfc822 content-type needs must have all of a
    message From:, Date:, and a destination address header present.  In
    contrast, the encapsulated headers of an embedded message/rfc822
    must have at least one of a message From:, Subject:, or Date:
    header.

    So, in the interests of not having a multipart in a multipart and
    thus keeping the table of contents with the digest, the Subject:
    header seems like a good candidate as the minimum header.

Point 3:

    In my digests the list of subjects is exactly that, just a list of
    the subject headers from the enclosed messages, one per line.
    However, I don't see any reason why a multipart/digest could not
    have exactly one part in it which was the list of subject header
    values with each one linked to the actual message, as suggested
    elsewhere on this mailing list.  In fact, I like this idea.

Point 4:

    Traditionally, digests have been formatted such that an explicit
    list of headers has been included.  In my digests I include all
    headers except Received: lines, believing those to be more space
    consuming than content rich as far as a digest is concerned.  Thus,
    an email client or archive technology has available to them all the
    information they need for replies or threading or whatever other
    functionality they wish to offer.

Comments, questions, or suggestions?

Jim




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