usefor-article-07 May 2002

5.4.  Subject

   The Subject-header contains a short string identifying the topic of
   the message. This is an inheritable header (4.2.5.2) to be copied
   into the Subject-header of any followup, in which case the new
   Subject-content SHOULD then default to the string "Re: " (a "back
   reference") followed by the contents of the pure-subject of the
   precursor. Any leading "Re: " in the pure-subject MUST be stripped.

      header              =/ Subject-header
      Subject-header      = "Subject" ":" SP Subject-content
      Subject-content     = [ [FWS] back-reference ] pure-subject
      pure-subject        = unstructured
      back-reference      = %x52.65.3A.20
                          ; which is a case-sensitive "Re: "

   The pure-subject MUST NOT begin with "Re: ".

        NOTE: The given syntax differs from that prescribed in [RFC
        2822] insofar as it does not permit a header content to be
        completely empty, or to consist of WSP only (see remarks in
        4.2.6 concerning undesirable headers).

   Followup agents MAY remove strings that are known to be used
   erroneously as back-reference (such as "Re(2): ", "Re:", "RE: ", or
   "Sv: ") from the Subject-content when composing the subject of a
   followup and add a correct back-reference in front of the result.

        NOTE: that would be "SHOULD remove instances" except that we
        cannot find a sufficiently robust and simple algorithm to do the
        necessary natural language processing.

   Followup agents MUST NOT use any other string except "Re: " as a back
   reference. Specifically, a translation of "Re: " into a local
   language or usage MUST NOT be used.

        NOTE: "Re" is an abbreviation for the Latin "In re", meaning "in
        the matter of", and not an abbreviation of "Reference" as is
        sometimes erroneously supposed.

   Agents SHOULD NOT depend on nor enforce the use of back references by
   followup agents. For compatibility with legacy news software the
   Subject-content of a control message (i.e. an article that also
   contains a Control-header) MAY start with the string "cmsg ", and
   non-control messages MUST NOT start with the string "cmsg ". See also
   section 6.13.

--- ../usefor-article-06/Subject.out          November 2001
+++ ../usefor-article-07/Subject.out          May 2002
@@ -1,14 +1,16 @@
 5.4.  Subject
 
-   The Subject header contains a short string identifying the topic of
-   the message. This is an inheritable header (4.2.2.2) to be copied
-   into the Subject header of any followup, in which case the new
-   header-content SHOULD then default to the string "Re: " (a "back
+   The Subject-header contains a short string identifying the topic of
+   the message. This is an inheritable header (4.2.5.2) to be copied
+   into the Subject-header of any followup, in which case the new
+   Subject-content SHOULD then default to the string "Re: " (a "back
    reference") followed by the contents of the pure-subject of the
    precursor. Any leading "Re: " in the pure-subject MUST be stripped.
 
-      Subject-content     = [ back-reference ] pure-subject
-      pure-subject        = 1*( [FWS] utext )
+      header              =/ Subject-header
+      Subject-header      = "Subject" ":" SP Subject-content
+      Subject-content     = [ [FWS] back-reference ] pure-subject
+      pure-subject        = unstructured
       back-reference      = %x52.65.3A.20
                           ; which is a case-sensitive "Re: "
 
@@ -17,7 +19,7 @@
         NOTE: The given syntax differs from that prescribed in [RFC
         2822] insofar as it does not permit a header content to be
         completely empty, or to consist of WSP only (see remarks in
-        4.2.5 concerning undesirable headers).
+        4.2.6 concerning undesirable headers).
 
    Followup agents MAY remove strings that are known to be used
    erroneously as back-reference (such as "Re(2): ", "Re:", "RE: ", or
@@ -39,7 +41,7 @@
    Agents SHOULD NOT depend on nor enforce the use of back references by
    followup agents. For compatibility with legacy news software the
    Subject-content of a control message (i.e. an article that also
-   contains a Control header) MAY start with the string "cmsg ", and
+   contains a Control-header) MAY start with the string "cmsg ", and
    non-control messages MUST NOT start with the string "cmsg ". See also
    section 6.13.