usefor-usepro-01 September 2004

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 user 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 [RFC 2822] style comments in headers do not affect serving and
       relaying agents (note that the Message-ID-, Newsgroups-,
       Distribution- and Path-headers do not contain them). They are
       unlikely to hinder their proper display in existing reading
       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 Newsgroups-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 possibility should be offered as a configurable option in
       relaying agents. User agents are unaffected.
     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 other 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 new Control: mvgroup command will need to be implemented in
       serving agents. For the benefit of older serving agents it is
       therefore RECOMMENDED that it be followed shortly by a
       corresponding newgroup command and it MUST always be followed by
       a rmgroup command for the old group after a reasonable overlap
       period. An implementation of the mvgroup command as an alias for
       the newgroup command would thus be minimally conforming. User
       agents are unaffected.
     o Provision is made for relaying and serving agents to use the
       Date-header in the case of articles injected through existing
       agents which do not provide an Injection-Date-header.
     o All the headers newly introduced by this standard can safely be
       ignored by existing software, albeit with loss of the new
       functionality.

--- ../usefor-usepro-00/Transitional_Arrangements.out          August 2004
+++ ../usefor-usepro-01/Transitional_Arrangements.out          September 2004