usefor-article-03 February 2000

6.13.2.3.  The Message-Version NNTP extension

   The following Service Extension to the NNTP protocol is defined in
   accordance with the framework set out in [NNTP], and is to be
   registered with IANA.

   Name of the extension:                             Message-Version
   Extension Label (for the LIST EXTENSIONS command): MESSAGE-VERSION
   Additional keywords, syntax and parameters:        None

   In a server supporting this extension, the behaviour of the ARTICLE,
   HEAD, BODY and STAT commands when the parameter is a <message-id> is
   modified as follows.

   If the specified article is available on the server then it (or its
   Head, Body or Status as appropriate) is returned in the normal
   manner.  Otherwise, if a leftmost id-left-side of the <message-id>
   (the part before the '@') contains "$v=<n>", where <n> is an integer
   version number, that "$v=<n>"and everything following it is stripped
   from that id-left-side and the article (Head, Body or Status) with
   the stripped <message-id> is returned instead.  Otherwise (no article
   is available under the original, or any stripped, <message-id>), a
   430 response is given as usual.

        NOTE: If the client is concerned to know whether the article
        found was exactly the one requested or a replacement article
        corresponding to a stripped <message-id>, then it has only to
        compare the <message-id> requested with that returned in the 220
        (221, 222, or 223) response. The intent of this extension is to
        enable the retrieval of the current version of an article (such
        as a regularly posted FAQ) referenced by a "news:" URL [RFC-
        1738] which quotes the <message-id> of an earlier version.

        NOTE: This extension has no effect on the IHAVE command.