rfc806.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

                                     17                          

                                                          Section 3.1.8



      Comments                 (OPTIONAL)

                This  field  permits  adding  comments  to  the message
                without  disturbing  the  original  contents   of   the
                message.
      Keywords                 (OPTIONAL)

                This  field  contains  keywords  or  phrases for use in
                retrieving a message.


      3.1.9  Extensions


           This message  format  specification  allows  two  additional
      types  of  fields,  vendor-defined  fields  and  as-yet-undefined
      (extension) fields that will be introduced by extensions to  this
      message format specification.


      vendor-defined-field
                Any   field   not   defined   in  this  message  format
                specification or any extension or successor to it is  a
                vendor-defined  field.  Names for vendor-defined fields
                could be preempted by extensions to this message format
                specification.

      extension-field
                Any field that is defined in a document published as  a
                formal  extension or replacement to this message format
                specification.



      3.2  Message Processing Functions


           A CBMS provides three basic classes of  functions,  creating
      messages,  transmitting  messages  to  their recipient, and post-
      receipt processing.  Although the  message  format  specification
      does  not define the number or nature of user functions in CBMSs,
      the meanings for the  fields  clearly  assume  certain  kinds  of
      functions.   For example, fields specifying recipients of replies
      to messages assume some kind of reply function; fields specifying
      message life span assume some kind of date processing functions.

           This section provides more detail  on  the  processing  that
      might be done by these kinds of functions, discussing the message
      fields  that  would  be  used  and  how they would be used.  (See
      summary in Table 1.)



                                     18                          

                                                          Section 3.2.1




      Processing Function    Fields Involved

      Message creation       Author, From, Sender, To,
        and posting          Cc, Bcc
      Message reissuing      Reissue-Type
      Reply generation       Reply-To
      Cross-referencing      Message-ID, In-Reply-To, References,
                             Obsoletes, Originator-Serial-Number
      Life span functions    Start-Date, End-Date,
                             Warning-Date
      Recipient processing   Circulate-To, Circulate-Next



      TABLE 1.  FIELDS USED IN MESSAGE PROCESSING FUNCTIONS


      3.2.1  Message creation and posting


           Messages  can  be  created  either  by reissuing an existing
      message to a new recipient (see Section 2.4.1) or by  creating  a
      new  message.    The  process of message creation might mean that
      some fields of a new message are filled in from the  contents  of
      some  other  message.  Reply functions (Section 3.2.3) provide an
      example of this.

           Different individuals could be involved in different  phases
      of  originating a message: creating it, taking responsibility for
      it, and explicitly interacting with a CBMS  to  send  it  to  its
      recipient.    One or more individuals may create (that is, write,
      but not necessarily enter into the CBMS) a message; they are said
      to be the message's authors, identified by the Author field.  One
      or more individuals may take responsibility for its contents  and
      the  decision  to post it; they are identified by the From field.
      One individual explicitly posts a given message; this  person  is
      called the message's sender (identified by the Sender field).

           The   sender  and  author(s)  are  often,  but  not  always,
      responsible for the message.  A common case in which  the  sender
      is not responsible for the message is when a secretary enters and
      posts  messages  for  someone else.  An example of a situation in
      which a message's author  is  not  responsible  for  the  message
      itself is when an administrative assistant prepares a report that
      is sent under a manager's signature.

           Messages  containing  Bcc  fields  are  treated specially by
      CBMSs.  The contents of this field are not included in copies  of
      the  message  sent  to the recipients designated in the To and Cc
      fields.  Some systems include the contents of the Bcc field  only


                                     19                          

                                                          Section 3.2.1



      in  the  originator's copy, others include include all or part of
      the Bcc field in the copies sent to the recipients  indicated  in
      the  Bcc  field.  This specification does not mandate how the Bcc
      field is to be treated.

           Audit trail entries (such as the  posting  time  and  sender
      identity)  are  automatically  appended  to a message by the CBMS
      each time the message passes through a posting slot to a  message
      transfer  system;  a  message  transfer system could also provide
      timestamps at each transfer between user agent and  the  transfer
      system.   A message identifier (Sections 3.2.4 and 3.1.6), placed
      in the message by the original sender's User Agent, is  preserved
      throughout  this  message  flow.    This means that when the same
      message is sent twice to the same recipients by the same  Sender,
      the audit trail information for the two messages is different.


      3.2.2  Message reissuing and forwarding


           Reissuing and forwarding both serve the general user goal of
      passing  a  message on to a new set of recipients.  Forwarding is
      the term used for an informal mechanism, which CBMSs implement by
      copying some or all of the original message into the contents  of
      a  field  in  the  new message.  Reissuing is the term used for a
      formal mechanism to ensure that the message being passed on never
      loses its integrity as a previously  sent  message.    CBMSs  use
      reissuing  to implement several different functions, depending on
      the purposes being served.


        o  Redistribution.  Make others aware of the  complete  and
           unaltered contents of the message.

        o  Assignment.    Delegate the responsibility for a message
           to somebody else.


      These purposes are exemplified in Figure 2.

           When a CBMS examines a forwarded message, it  cannot  always
      distinguish  the  old  message  from  what  was  added  when  the
      forwarding took place.  In addition,  the  forwarded  information
      might  no  longer  have  the  form of a message.  This is usually
      because the format of the message has been changed (for  example,
      to pure unformatted text).  (See Figure 2 for an example of how a
      CBMS  might  forward a message.)  In contrast, a reissued message
      can always be separated from  its  enclosing  message  and  never
      loses its identity as a correctly formed message.

           This  specification  provides  the  Reissue-Type  field  for


                                     20                          

                                                          Section 3.2.2




                            The Original Message
      John Doe wishes Jane Jones to get a copy of the following
      message:
                      Message:
                        Field: From "Jean Smith"
                        Field: Posted-Date "15 June 1980"
                        Field: To "John Doe"
                        Field: Subject "Next sales meeting"
                        Field: Text "The agenda for ..."

                               Redistribution
      Message:
        Field: From "John Doe"                  John Doe is responsible
        Field: Posted-Date "16 June 1980"       for the redistribution.
        Field: To "Jane Jones"
        Field: Reissue-Type "Redistribution"    This message directly
        Message:                                incorporates a
          Field: From "Jean Smith"              redistributed message.
          Field: Posted-Date "15 June 1980"
          Field: To "John Doe"
          Field: Subject "Next Sales Meeting"
          Field: Text "The agenda for ..."

                                 Forwarding
      Message:
        Field: From "John Doe"
        Field: Posted-Date "16 June 1980"
        Field: To "Jane Jones"
        Field: Text                             A realization of the
          "From Jean Smith                      original message is
           To John Doe                          copied into the Text field.
           Sent on 15 June 1980                 Note that John's CBMS
           Subject Next Sales Meeting           has chosen to represent
                                                it as a text string.
           The agenda for ..."



      FIG. 2.  MESSAGE FORWARDING AND REDISTRIBUTION













                                     21                          

                                                          Section 3.2.2



      supporting re-issuing.  Forwarding, since it is an informal means
      of  serving  the  purpose  of  passing  on  information,  has  no
      supporting fields in the specification.

           This specification provides for  reissuing  of  messages  by
      encapsulating.    This  method embeds the entire original message
      inside a new message.  Encapsulating adds  structure  around  the

             2
      message .  This allows any part of it to be easily extracted.

           Authentication is an organizational policy issue  associated
      passing  on  previously  sent  messages.   Each organization must
      decide if the CBMS it acquires should support reissuing or simply
      supply forwarding.


      3.2.2.1  Redistribution

           Redistribution is a CBMS function for sending  the  original
      contents  of a message intact and unchanged to new recipients.  A
      redistributed message is identical to the original  message  with
      the  exception  of  added  information  about the reissuing.  For
      reissuing with this purpose, the Reissue-Type field contains  the
      ASCII  string  "Redistribution".    The original message has been
      included directly in a new message.  (See Figure 2.)


      3.2.2.2  Assignment

           Assignment is the process of designating responsibility.  In
      some organizations, formal message traffic  is  funneled  through
      one  or  more parts of the organization (called offices) where it
      is directed to the appropriate individuals or other  offices  for
      final  disposition.    Assignment  is done by reissuing a message
      with  the  Reissue-Type  field  containing   the   ASCII   string
      "Assigned."    A  message  which  contains  this  field  is to be
      interpreted as meaning that the addressees in the "To" field have
      had the reissued message assigned to them for some action.    Any
      addressee  in  the  "Cc"  field  has had the message assigned for
      information.  The "From" field records who assigned  the  message
      and   the  "Posted-Date"  field  records  when  the  message  was
      assigned.


      _______________

        2
         A message can contain another message, and  that  message  can
      contain another message, and so on to any depth of encapsulating.
      This can occur by reissuing a message repeatedly.


                                     22                          

                                                          Section 3.2.3



      3.2.3  Reply generation


           Reply  generation  involves creating a new message in direct
      reply to some other message by drawing on the contents of  fields
      in  the  other  message  to fill fields in the new message.  Many
      CBMSs  provide  reply  facilities  that  determine  the  intended
      recipients of a reply to a message.


        o  A  Reply-To  field  is  defined  by  this message format
           specification.   When  a  message  contains  a  Reply-To
           field,  the  CBMS  should send replies to the recipients
           designated in the  Reply-To  field  instead  of  to  the
           recipients designated in the From field.  This statement
           applies  to  original  messages  only,  not  to reissued
           messages.  The message  format  specification  makes  no
           recommendations concerning replies to reissued messages.

           Reply-To has several possible applications.


             1.  The  individual(s)  responsible  for  the  message
                 might not have regular access to a CBMS and  would
                 indicate  an  alternate  recipient, for example, a
                 secretary.

             2.  The people  responsible  for  receiving  responses
                 might  not  be the people who were responsible for
                 creating the message.

             3.  Discussion and conference groups  could  use  this
                 feature  to  ensure  correct  distribution  of any
                 submission by having the conference  group  itself
                 designated in the Reply-To field.


        o  When  the message does not contain a Reply-To field, the
           recipient should reply to the originators enumerated  in
           the  From  field.   The sender and authors should not be
           added automatically to the list of those  receiving  the
           reply.


           Replies  could  also  be sent to the other recipients of the
      original  message.    Vendors  might   o