usefor-article-04 April 2001

3.2.  Transitional Arrangements

   An important distinction must be made between serving and relaying
   agents which are responsible for the distribution and storage of news
   articles, and user agents which are responsible for interactions with
   users. It is important that the former should be upgraded to conform
   to this standard as soon as possible to provide the benefit of the
   enhanced facilities.  Fortunately, the number of distinct
   implementations of such agents is rather small, at least so far as
   the main "backbone" of Usenet is concerned, and many of the new
   features are already supported. Contrariwise, there are a great
   number of implementations of user agents, installed on a vastly
   greater number of small sites. Therefore, the new functionality has
   been designed so that existing agents may continue to be used,
   although the full benefits may not be realised until a substantial
   proportion of them have been upgraded.
   In the list which follows, care has been taken to distinguish the
   implications for both kinds of agent.

     o [MESSFOR] style comments in headers do not affect serving and
       relaying agents (note that the Newsgroups and Path headers do not
       contain them). They are unlikely to hinder their proper display
       in existing user agents except in the case of the References
       header in agents which thread articles. Therefore, it is provided
       that they SHOULD NOT be generated except where permitted by the
       previous standards.
     o Because of its importance to all serving agents, the extension
       permitting whitespace and folding in Newsgroup headers SHOULD NOT
       be used until it has been widely deployed amongst relaying
       agents. User agents are unaffected.
     o The new style of Path header is already consistent with the
       previous standards. However, the intention is that relaying
       agents should eventually reject articles in the old style, and so
       this should be offered as a configurable option for relaying
       agents. User agents are unaffected.
     o The vast majority of serving, relaying and transport agents are
       believed to be already 8bit clean (in the slightly restricted
       sense in which that term is used in the MIME standards). User
       agents that do not implement MIME may be disadvantaged, but no
       more so than at present when faced with 8bit characters (which
       currently abound in spite of the previous standards).
     o The introduction of MIME reflects a practice that is already
       widespread.  Articles in strict compliance with the previous
       standards (using strict US-ASCII) will be unaffected. Many user
       agents already support it, at least to the extent of widely used
       charsets such as ISO-8859-1. Users expecting to read articles
       using the more exotic charsets will need to acquire suitable
       reading agents. It is not intended, in general, that any single
       user agent will be able to display every charset known to IANA,
       but all such agents MUST support US-ASCII. Serving and relaying
       agents are not affected.
     o The use of the UTF-8 charset for headers will not affect any
       existing usage, since US-ASCII is a strict subset of UTF-8.
       Insofar as newsgroup names containing non-ASCII characters can
       now be expected to arise, support from serving and relaying
       agents will be necessary. It is believed that the customary
       storage structure used by serving agents can already cope
       (perhaps not ideally) with such names. Note that it is not
       necessary for serving and relaying agents to understand all the
       characters available in UTF-8, though it is desirable for them to
       be displayable for diagnostic purposes via some escape mechanism
       using, for example, the visible subset of US-ASCII. For users
       expecting to use the more exotic charsets available under UTF-8,
       the remarks already made in connection with MIME will apply.
     o The new Control: mvgroup command will need to be implemented in
       serving agents. It SHOULD be used in conjunction with pairs of
       matching rmgroup and newgroup commands (injected shortly after
       the mvgroup) until such time as mvgroup is widely implemented.
       The new Replaces header is also effectively a Control command,
       and transitional arrangements are provided which should be used
       in the meantime. User agents are unaffected.
     o The headers newly introduced by this standard can safely be
       ignored by existing software, albeit with loss of the new
       functionality.

--- ../usefor-article-03/Transitional_Arrangements.out          February 2000
+++ ../usefor-article-04/Transitional_Arrangements.out          April 2001
@@ -14,9 +14,9 @@
    been designed so that existing agents may continue to be used,
    although the full benefits may not be realised until a substantial
    proportion of them have been upgraded.
-
    In the list which follows, care has been taken to distinguish the
    implications for both kinds of agent.
+
      o [MESSFOR] style comments in headers do not affect serving and
        relaying agents (note that the Newsgroups and Path headers do not
        contain them). They are unlikely to hinder their proper display
@@ -30,11 +30,9 @@
        agents. User agents are unaffected.
      o The new style of Path header is already consistent with the
        previous standards. However, the intention is that relaying
-       agents should henceforth reject articles in the old style, and so
+       agents should eventually reject articles in the old style, and so
        this should be offered as a configurable option for relaying
        agents. User agents are unaffected.
-[Should that "should" be a "SHOULD" or a "MAY".]
-
      o The vast majority of serving, relaying and transport agents are
        believed to be already 8bit clean (in the slightly restricted
        sense in which that term is used in the MIME standards). User