usefor-article-03 February 2000

6.13.2.4.  Examples

   Example 1. The first edition of a FAQ is posted with a message
   identifier of the form:  <examplegroup-faq@faq-site.example>. The
   next (but identical) version, a month later, has:

      Message-ID: <examplegroup-faq$v=1$A1b@faq-site.example>
      Replaces: <examplegroup-faq@faq-site.example> ; usage=repost
      Supersedes: <examplegroup-faq@faq-site.example>
   Observe the inclusion of a Supersedes header as well, it being
   presumed that the Replaces header was not yet widely implemented at
   that time.

   The next one, another month later (and with some significant changes
   justifying the use of "replace" rather than "repost") has:

      Message-ID: <examplegroup-faq$v=2$B2b@faq-site.example>
      Replaces: <examplegroup-faq$v=1$A1b@faq-site.example>
         <examplegroup-faq@faq-site.example> ; usage=replace
      Supersedes: <examplegroup-faq$v=1$A1b@faq-site.example>

   The next one, another month later, has:

      Message-ID: <examplegroup-faq$v=3$C3c@faq-site.example>
      Replaces: <examplegroup-faq$v=2$B2b@faq-site.example>
         <examplegroup-faq$v=1$A1b@faq-site.example> ; usage=repost
      Supersedes: <examplegroup-faq$v=2$B2b@faq-site.example>

   Note that the only reason to include more than one message identifier
   in the Replaces is in case a site had missed the previous
   Replacement. It is hardly necessary with such a long interval between
   the postings.

   Under the above, on systems using the version-number system (which is
   optional) requests for any message identifier in the chain will
   always return the most recent. As such the URL "news:examplegroup-
   faq@faq-site.example" will always work, making it suitable to appear
   in HTML documents.

   Example 2. A user posts a message <myuniquepart@mysite.example> to
   the net.  She notices a typo and, 2 minutes later, posts with:

      Message-ID: <myuniquepart$v=1$xxx@mysite.example>
      Replaces: <myuniquepart@mysite.example> ; usage=revise
   3 minutes later she sees another typo, and posts:

      Message-ID: <myuniquepart$v=2$yyy@mysite.example>
      Replaces: <myuniquepart$v=1$xxx@mysite.example>
         <myuniquepart@mysite.example> ; usage=revise

   The two bad versions will be replaced with the 3rd, even if a site
   never sees the 2nd due to batching or feed problems (thus the use of
   two message identifiers is quite useful in this case, in
   contradistinction to the first example). Requests for the original
   will return the 3rd.