usefor-article-10 April 2003

6.15.  Supersedes

   The Supersedes-header contains a message identifier specifying an
   article to be superseded upon the arrival of this one. The specified
   article MUST be treated as though a "cancel" control message had
   arrived for the article (but observe that a site MAY choose not to
   honour a "cancel" message, especially if its authenticity is in
   doubt). The content syntax makes use of syntax defined in [RFC 2822],
   subject to the same revisions as in 5.3.

      header              =/ Supersedes-header
      Supersedes-header   = "Supersedes" ":" SP Supersedes-content
      Supersedes-content  = [CFWS] msg-id [CFWS]

        NOTE: There is no "c" in "Supersedes".

        NOTE: The Supersedes-header defined here has no connection with
        the Supersedes-header that sometimes appears in Email messages
        converted from X.400 according to [RFC 2156]; in particular, the
        syntax here permits only one msg-id in contrast to the multiple
        msg-ids in that Email version.

   Thus when an article contains a Supersedes-header, the old article
   mentioned SHOULD be withdrawn from circulation or access, as in a
   cancel message (7.3), and the new article inserted into the system as
   any other new article would have been.

   Whatever security or authentication checks are normally applied to a
   Control cancel message (or may be prescribed for such messages by
   some extension to this standard - see the remarks in 7.1 and 7.3)
   MUST also be applied to an article with a Supersedes-header. In the
   event of the failure of such checks, the article SHOULD be discarded,
   or at most stored as an ordinary article.

--- ../usefor-article-09/Supersedes.out          February 2003
+++ ../usefor-article-10/Supersedes.out          April 2003