usefor-article-03 February 2000

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
   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 )
      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 [MESSFOR]
        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).

   Followup agents MAY remove instances of non-standard 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 6.11.

--- ../s-o-1036/Subject.out          June 1994
+++ ../usefor-article-03/Subject.out          February 2000
@@ -1,66 +1,44 @@
 5.4. Subject
 
-The  Subject header's content (the "subject" of the article)
-is a short phrase describing the topic of the article:
-
-     Subject-content  = [ "Re: " ] nonblank-text
-
-Encoded words MAY appear in this header.
-
-If the article is a followup, the subject SHOULD begin  with
-"Re: "  (a  "back reference").  If the article is not a fol-
-lowup, the subject MUST not begin  with  a  back  reference.
-Back references are case-insensitive, although "Re: " is the
-preferred form.  A followup  agent  assisting  a  poster  in
-preparing a followup SHOULD prepend a back reference, UNLESS
-the subject already begins with one.  If the  poster  deter-
-mines  that  the topic of the followup differs significantly
-from what is described in the subject, a new, more  descrip-
-tive,  subject  SHOULD  be  substituted (with no back refer-
-ence).  An article whose subject begins with a  back  refer-
-ence  MUST  have a References header referencing the precur-
-sor.
-
-     NOTE: A back reference  is  FOUR  characters,  the
-     fourth being a blank.  RFC 1036 was confused about
-     this.  Observe also that only ONE  back  reference
-     should be present.
-
-     NOTE:  There  is a semi-standard convention, often
-     used, in which a subject change is flagged by mak-
-     ing the new Subject-content of the form:
-
-          new topic (was: old topic)
-
-     possibly  with  "old  topic"  somewhat  truncated.
-     Posters wishing to  do  something  like  this  are
-     urged  to  use  this exact form, to simplify auto-
-     mated analysis.
-
-For historical reasons, the  subject  MUST  not  begin  with
-"cmsg " (note that this sequence ends with a blank).
-
-     NOTE:  Some  old  news  software  takes  a subject
-     beginning with "cmsg " as an indication  that  the
-     article is a control message (see sections 6.6 and
-     7).  This mechanism is obsolete  and  undesirable,
-     but accidental triggering of it is still possible.
-
-The subject SHOULD be terse.  Posters SHOULD avoid trying to
-cram  their  entire  article into the headers; even the sim-
-plest query usually benefits  from  a  sentence  or  two  of
-
-INTERNET DRAFT to be        NEWS                    sec. 5.4
-
-
-elaboration  and  context, and the details of header display
-vary widely among reading agents.
-
-     NOTE: All-in-the-subject  articles  are  sometimes
-     the  result of misunderstandings over the interac-
-     tion protocol of a posting agent.  Posting  agents
-     might wish to give special attention to the possi-
-     bility that a poster specifying a very  long  sub-
-     ject  might have thought he was typing the body of
-     the article.
+   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
+   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 )
+      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 [MESSFOR]
+        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).
+
+   Followup agents MAY remove instances of non-standard 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 6.11.