RFC #  822

     Obsoletes:  RFC #733  (NIC #41952)


                        STANDARD FOR THE FORMAT OF

                        ARPA INTERNET TEXT MESSAGES






                              August 13, 1982






                                Revised by

                             David H. Crocker


                      Dept. of Electrical Engineering
                 University of Delaware, Newark, DE  19711
                      Network:  DCrocker @ UDel-Relay



                                  PREFACE

                                    (略)

     1.  INTRODUCTION

     1.1.  SCOPE

          This standard specifies a syntax for text messages that  are
     sent  among  computer  users, within the framework of "electronic
     mail".  The standard supersedes  the  one  specified  in  ARPANET
     Request  for Comments #733, "Standard for the Format of ARPA Net-
     work Text Messages".

          In this context, messages are viewed as having  an  envelope
     and  contents.   The  envelope  contains  whatever information is
     needed to accomplish transmission  and  delivery.   The  contents
     compose  the object to be delivered to the recipient.  This stan-
     dard applies only to the format and some of the semantics of mes-
     sage  contents.   It contains no specification of the information
     in the envelope.

          However, some message systems may use information  from  the
     contents  to create the envelope.  It is intended that this stan-
     dard facilitate the acquisition of such information by programs.

          Some message systems may  store  messages  in  formats  that
     differ  from the one specified in this standard.  This specifica-
     tion is intended strictly as a definition of what message content
     format is to be passed BETWEEN hosts.

     Note:  This standard is NOT intended to dictate the internal for-
            mats  used  by sites, the specific message system features
            that they are expected to support, or any of  the  charac-
            teristics  of  user interface programs that create or read
            messages.

          A distinction should be made between what the  specification
     REQUIRES  and  what  it ALLOWS.  Messages can be made complex and
     rich with formally-structured components of information or can be
     kept small and simple, with a minimum of such information.  Also,
     the standard simplifies the interpretation  of  differing  visual
     formats  in  messages;  only  the  visual  aspect of a message is
     affected and not the interpretation  of  information  within  it.
     Implementors may choose to retain such visual distinctions.

          The formal definition is divided into four levels.  The bot-
     tom level describes the meta-notation used in this document.  The
     second level describes basic lexical analyzers that  feed  tokens
     to  higher-level  parsers.   Next is an overall specification for
     messages; it permits distinguishing individual fields.   Finally,
     there is definition of the contents of several structured fields.


     1.2.  COMMUNICATION FRAMEWORK

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