rfc767.txt

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RFC:767
                                    
                                    
                                    
                                    
                                    
                                    
     A STRUCTURED FORMAT FOR TRANSMISSION OF MULTI-MEDIA DOCUMENTS
                                    
                                    
                                    
                           Jonathan B. Postel


















                              August 1980
                                    
                                    
                                    
                                    
                     Information Sciences Institute
                   University of Southern California
                           4676 Admiralty Way
                   Marina del Rey, California  90291

                             [phone]


< INC-PROJECT, MMMSFS.NLS.21, >, 5-Sep-80 20:19 JBP ;;;;






















































                                                                  Postel


August 1980                                                             
           A Structured Format for Transmission of Multi-Media Documents



                           TABLE OF CONTENTS

    PREFACE ........................................................ iii

1.  INTRODUCTION ..................................................... 1

  1.1.  Motivation ................................................... 1
  1.2.  Scope ........................................................ 1
  1.3.  Terminology .................................................. 1
  1.4.  Document Description ......................................... 2
  1.5.  Other Work ................................................... 2

2.  SPECIFICATION .................................................... 3

  2.1.  Document ..................................................... 3
  2.2.  Message Objects  ............................................. 5
  2.3.  Body Structures ............................................. 13
  2.3.1.  Simple Elements ........................................... 13
  2.3.2.  Structured Text ........................................... 13
  2.3.3.  NLS File Example .......................................... 13
  2.3.4.  Multimedia Structures ..................................... 15
  2.3.5.  The Media ................................................. 21
  2.3.6.  TEXT ...................................................... 22
  2.3.7.  VOICE ..................................................... 22
  2.3.8.  FACSIMILE ................................................. 23
  2.3.9.  GRAPHICS .................................................. 24

3.  EXAMPLES & SCENARIOS ............................................ 25

  Example 1:  Text Example .......................................... 25
  Example 2:  Multimedia Example .................................... 28

REFERENCES .......................................................... 31

  
















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           A Structured Format for Transmission of Multi-Media Documents



                                PREFACE



This is the first edition of this format specification and should be
treated as a request for comments, advice, and suggestions.  A great
deal of prior work has been done on computer aided message systems and
some of this is listed in the reference section.  This specification was
shaped by many discussions with members of the ARPA research community,
and others interested in the development of computer aided message
systems.  This document was prepared as part of the ARPA sponsored
Internetwork Concepts Research Project at ISI.

                                                              Jon Postel





































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           A Structured Format for Transmission of Multi-Media Documents






















































Postel                                                         [Page iv]



RFC: 767                                                       J. Postel
                                                                 USC-ISI
                                                             August 1980




     A STRUCTURED FORMAT FOR TRANSMISSION OF MULTI-MEDIA DOCUMENTS



                            1.  INTRODUCTION

This document describes a format for transmitting structured data
representations of multimedia documents.  This format is intended to be
used with the Internet Message Protocol in an internetwork message
delivery system.  That system is designed to transmit messages between
processes in host computers called Message Processing Modules (MPMs).
MPMs are located in several networks and together constitute an
internetwork message delivery system.  The Internet Message Protocol
defines a message as being composed of an Identification, a Command, and
a Document.  This report is intended to define the format of such
Documents.  The reader is assumed to be familiar with the Internet
Message Protocol [1].

1.1.  Motivation

  Computer applications are being implemented which interact with users
  in a variety of media (text, graphics, facsimile, speech).  As
  computer devices become available to process multimedia information it
  becomes desirable to use computers to exchange multimedia information
  between programs and users via various mechanisms including computer
  mail.

1.2.  Scope

  This format is intended to be used for the transmission of multimedia
  documents in the internetwork message delivery system, but it is
  thought that it has a wider applicability.

1.3.  Terminology

  The messages are routed by a process called the Message Processing
  Module or MPM.  Messages are created and consumed by User Interface
  Programs (UIPs) in conjunction with users.

  The basic unit transferred between MPMs is called a message.  A
  message is made up of a transaction identifier (which uniquely
  identifies the message), a command (which contains the necessary
  information for delivery), and document.  The document is a data
  structure.

  For a personal letter the document body corresponds to the contents of


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Introduction



  the letter; the document header corresponds to the date line,
  greeting, and signature.

  For an inter-office memo the document body corresponds to the text;
  the document header corresponds to the header of the memo.

  The commands correspond to the information used by the Post Office or
  the mail room to route the letter or memo.  Some of the information in
  the command is supplied by the UIP.

1.4.  Document Description

  The document is composed of fields.  Each field will carry an
  identifying name.  Typical fields are DATE, TO, SUBJECT, and BODY.
  Most of the fields will be very simple, some will be complex.  The
  body field may be quite complex.  For example, the DATE is a very
  constrained character string specifying the date and time in ISO
  format. A more complex example is the TO field which is a list of
  mailboxes, where a mailbox is itself a property list of address
  information items.  The BODY may be simply a character string, or a
  very structured collection of data representing information in
  different media.

  The BODY may be structured to indicate a controlled presentation of
  multimedia information.  There is provision for the inclusion of text,
  graphics, facsimile, and voice information in the body of documents.
  The presentation of information units may sequential, independent, or
  simultaneous.

1.5.  Other Work

  This protocol the benefited from the earlier work on message protocols
  in the ARPA Network [2,3,4,5,6], and the ideas of others about the
  design of computer message systems [7,8,9,10,11,12,13,14,15,16,17,18].
















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                           2.  SPECIFICATION

The structured format of a document is built on the basic data elements
used in the Internet Message Protocol [1].

2.1.  Document

  The document is a property list of <name,value> pairs called fields.
  A few fields are specifically required and many are optional.  Some of
  the field values are simple and a few are quite complicated.  In
  particular the body value may be highly structured.

  Older message systems have considered the document to be divided into
  a header and a body, and have used keywords to indicate specific
  header fields (e.g., date, to, subject).  Roughly speaking, this
  functionality is provided in this new structured format by considering
  the name part of the <name,value> pair to be a keyword.  In addition,
  this new structured format eliminates the separate treatment of the
  body.

  It is impossible to foresee the many forms documents will take so the
  standard for a document header must be flexible.  The approach here is
  to define a set of basic fields and allow addition of whatever fields
  are necessary.  Features added in this fashion may not be understood
  by others.

  The minimum document is a property list of the following fields:

    Name     Value
    ----     -----
    DATE     date string (name)
    SENDER   a mailbox
    SUBJECT  subject string (text)
    BODY     a data structure

  A typical document is a property list containing the following fields:

    Name     Value
    ----     -----
    DATE     date string (name)
    SENDER   a mailbox
    FROM     list of mailboxes
    TO       list of mailboxes
    CC       list of mailboxes
    SUBJECT  subject string (text)
    BODY     a data structure





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Specification



  An elaborate document might contain the following fields:

    Name        Value
    ----        -----
    DATE        date string (name)
    SENDER      a mailbox
    FROM        list of mailboxes
    TO          list of mailboxes
    CC          list of mailboxes
    BCC         list of mailboxes
    REPLY-TO    list of mailboxes
    SUBJECT     subject string (text)
    COMMENTS    comment string (text)
    MESSAGE-ID  message identifier of this message (text)
    IN-REPLY-TO message identifier of previous message (text)
    REFERENCES  message identifiers of other messages (text)
    KEYWORDS    key terms used in this message (text)
    BODY        a data structure

  One of the key objects is the mailbox.  It appears in the sender,
  from, to, cc, bcc, and reply-to fields.  The mailbox is a property
  list of objects that combine to specify a destination recipient for a
  message.  Most of the <name,value> pairs that make up a mailbox are
  identical to those used in the deliver command in the Internet Message
  Protocol [1].  A few additional <name,value> pairs are defined for use
  in a mailbox in the document context.  In particular, there is a field
  for the real name of a person in contrast to the "user name" which
  identifies a computer account.

  In addition there is a field to specify a distribution group name.
  Such group names are used to indicate that a document is being sent to
  a group of recipients.  This essentially presents an alternate form
  for a mailbox which consists of the single <name,value> pair for the
  group name.  There is no required relationship between a group name
  mailbox and other mailboxes in the same list.

  For example, all of the following situations are allowed:

    .  a mailbox list consisting of a single mailbox specifying a
       particular user,

    .  a mailbox list consisting of a single mailbox with a group name,

    .  a mailbox list consisting of a mailbox with a group name and a
       mailbox specifying a particular user, with either the user in or
       not in the group,

    .  a mailbox list consisting of a mailbox with a group name and a


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                                                           Specification



       several mailboxes specifying a particular users, with some users
       in the group and some not,

    .  a mailbox list consisting of several mailboxes specifying group
       names and a several mailboxes specifying a particular users, with