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RFC 841 - Specification for message format for Computer Based Me


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      RFC 841

      FIPS Pub 98

      SPECIFICATION FOR MESSAGE FORMAT FOR COMPUTER
      BASED MESSAGE SYSTEMS

      27 January 1983

      National Bureau of Standards

      This RFC is FIPS 98.  The purpose of distributing this document
      as an RFC is to make it easily accesible to the ARPA research
      community.  This RFC does not specify a standard for the ARPA
      Internet.

                              TABLE OF CONTENTS

                                                                   Page

      EXECUTIVE SUMMARY                                               5

      1.  INTRODUCTION                                                7

          1.1  Guide to Reading This Document                         7
          1.2  Vendor-Defined Extensions to the Specification         8
          1.3  The Scope of the Message Format Specification          8
          1.4  Issues Not Within the Scope of the Message Format      8
               Specification
          1.5  Relationship to Other Efforts                          9

      2.  A SIMPLE MODEL OF A CBMS ENVIRONMENT                       10

          2.1  Logical Model of a CBMS                               12
          2.2  Relationship to the ISO Reference Model for Open      14
               Systems Interconnection
          2.3  Messages and Fields                                   14
          2.4  Message Originators and Recipients                    15

      3.  SEMANTICS                                                  17

          3.1  Semantics of Message Fields                           17
               3.1.1  Types of fields                                17
               3.1.2  Semantic Compliance Categories                 18
               3.1.3  Originator fields                              18
               3.1.4  Recipient fields                               19
               3.1.5  Date fields                                    20
               3.1.6  Cross-reference fields                         21
               3.1.7  Message-handling fields                        22
               3.1.8  Message-content fields                         23
               3.1.9  Extensions                                     23

                                      i

          3.2  Message Processing Functions                          24
               3.2.1  Message creation and posting                   24
               3.2.2  Message reissuing and forwarding               25
                    3.2.2.1  Redistribution                          26
                    3.2.2.2  Assignment                              28
               3.2.3  Reply generation                               28
               3.2.4  Cross-referencing                              29
                    3.2.4.1  Unique identifiers                      29
                    3.2.4.2  Serial numbering                        30
               3.2.5  Life span functions                            30
               3.2.6  Requests for recipient processing              31
                    3.2.6.1  Message circulation                     31
          3.3  Multiple Occurrences and Ordering of Fields           31

      4.  SYNTAX                                                     34

          4.1  Introduction                                          34
               4.1.1  Message structure                              34
               4.1.2  Data elements                                  35
                    4.1.2.1  Primitive data elements                 36
                    4.1.2.2  Constructor data elements               36
               4.1.3  Properties                                     36
                    4.1.3.1  Printing-names                          37
                    4.1.3.2  Comments                                37
               4.1.4  Data compression and encryption                37
          4.2  Overview of Syntax Encoding                           37
               4.2.1  Identifier Octets                              38
               4.2.2  Length code and Qualifier components           39
                    4.2.2.1  Length Codes                            41
                    4.2.2.2  Qualifier                               42
               4.2.3  Property-List                                  44
               4.2.4  Data Element Contents                          44
          4.3  Data Element Syntax                                   44
               4.3.1  Data elements                                  45
                    4.3.1.1  Primitives                              47
                    4.3.1.2  Constructors                            49
                    4.3.1.3  Data Elements that Extend this Speci-   52
                             fication
               4.3.2  Using data elements within message fields      53
               4.3.3  Properties and associated elements             54
               4.3.4  Encryption identifiers                         54
               4.3.5  Compression identifiers                        54
               4.3.6  Message types                                  55

                                     ii

      SUMMARY OF APPENDIXES                                          56

      APPENDIX A.  FIELDS -- IMPLEMENTORS' MASTER REFERENCE          57

      APPENDIX B.  DATA ELEMENTS -- IMPLEMENTORS' MASTER REFERENCE   63

      APPENDIX C.  DATA ELEMENT IDENTIFIER OCTETS                    71

      APPENDIX D.  SUMMARY OF MESSAGE FIELDS BY COMPLIANCE CATE-     72
                   GORY

          D.1  REQUIRED Fields                                       72
          D.2  BASIC Fields                                          72
          D.3  OPTIONAL Fields                                       72

      APPENDIX E.  SUMMARY OF MESSAGE SEMANTICS BY FUNCTION          74

          E.1  Circulation                                           74
          E.2  Cross-Referencing                                     74
          E.3  Life Spans                                            74
          E.4  Delivery System                                       74
          E.5  Miscellaneous Fields Used Generally                   75
          E.6  Reply Generation                                      75
          E.7  Reissuing                                             75
          E.8  Sending (Normal Transmission)                         75

      APPENDIX F.  SUMMARY OF DATA ELEMENT SYNTAX                    76

      APPENDIX G.  SUMMARY OF DATA ELEMENTS BY COMPLIANCE CATEGORY   78

          G.1  BASIC Data Elements                                   78
          G.2  OPTIONAL Data Elements                                78

                                     iii

      APPENDIX H.  EXAMPLES                                          80

          H.1  Primitive Data Elements                               80
          H.2  Constructor Data Elements                             82
          H.3  Data Elements that Extend this Specification          87
          H.4  Fields                                                88
          H.5  Messages                                              90
          H.6  Unknown Lengths                                       94
          H.7  Message Encoding Using Vendor-Defined Fields          97
               H.7.1  Example of a JANAP-128 Message                 97
               H.7.2  Encoding of Example using the FIPS Message     97
                      Format
               H.7.3  Field Mappings of JANAP-128 to FIPS Format    101
               H.7.4  Vendor-Defined Fields                         101

      REFERENCES                                                    103

      INDEX                                                         105

                                     iv

                               LIST OF FIGURES

      FIG. 1.    LOGICAL MODEL OF A COMPUTER-BASED MESSAGE SYSTEM    12
      FIG. 2.    MESSAGE FORWARDING AND REDISTRIBUTION               27
      FIG. 3.    EXAMPLE OF MESSAGE CIRCULATION                      32
      FIG. 4.    STRUCTURE OF IDENTIFIER OCTETS                      39
      FIG. 5.    ENCODING MECHANISM FOR QUALIFIERS AND LENGTH        40
                 CODES
      FIG. 6.    REPRESENTATION OF LENGTH CODES                      42
      FIG. 7.    EXAMPLES OF QUALIFIER VALUES                        43

                                      v

                               LIST OF TABLES

      TABLE 1.    FIELDS USED IN MESSAGE PROCESSING FUNCTIONS        24
      TABLE 2.    HIGH-ORDER BITS IN THE IDENTIFIER OCTET            39

                                     vi

                             Federal Information
                     Processing Standards Publication 98
                               27 January 1983
                         Announcing the Standard for

                               MESSAGE FORMAT
                                     FOR
                       COMPUTER BASED MESSAGE SYSTEMS

      Federal  Information Processing Standards Publications are issued
      by the National Bureau of Standards pursuant to section 111(f)(2)
      of the Federal Property and Administrative Services Act of  1949,
      as  amended,  Public  Law 89-306 (79 Stat. 1127), Executive Order
      11717 (38 FR 12315, dated May 11, 1973), and Part 6 of  Title  15
      Code of Federal Regulations (CFR).

      Name  of  Standard.  Message  Format  for  Computer Based Message
      Systems (FIPS PUB 98).

      Category of Standard. Software Standard; Interchange Codes, Media
      and Data Files.

      Explanation.  This  standard  separates  information  so  that  a
      Computer  Based  Message  System  can  locate and operate on that
      information (which is found in the fields of messages).  This  is
      the  first of a family of standards which will ensure information
      interchange among Computer Based Message Systems.

      Approving Authority. Secretary of Commerce

      Maintenance Agency. Department of Commerce,  National  Bureau  of
      Standards (Institute for Computer Sciences and Technology).

      Cross Index. Not Applicable.

      Related Documents.

         a. American   National   Standard   Code  for  Information
            Interchange (ASCII), X3.4-1977,FIPS PUBS 1-1.

         b. American National Standard  Code  Extension  Techniques
            for  Use with the 7-bit Coded Character Set of American
            National  Standard   Code   (ASCII)   for   Information
            Interchange, X3.41-1974, FIPS PUB 35.

         c. National  Bureau  of Standards.  Calendar Date. Federal
            Information Processing Standards  Publication  4,  U.S.

                                      1

            Department  of Commerce / National Bureau of Standards,
            November, 1968.

         d. National Bureau of Standards. Data Encryption Standard.
            Federal Information  Processing  Standards  Publication
            46,  U.S.  Department  of  Commerce/National  Bureau of
            Standards, January, 1977.

         e. National Bureau of Standards. Representation  of  Local
            Time  of  the  Day for Information Interchange. Federal
            Information Processing Standards Publication  58,  U.S.
            Department  of Commerce / National Bureau of Standards,
            February 1979.

         f. National  Bureau  of   Standards.   Representation   of
            Universal  Time,  Local  Time Differentials, and United
            States   Time   Zone   References    for    Information
            Interchange.  Federal  Information Processing Standards
            Publication 59, U.S. Department of Commerce /  National
            Bureau of Standards, February, 1979.

      Applicability.  This  message  format standard applies to Federal
      departments  and  agencies  in  their  acquisition  and  use   of
      computer-based  message  systems (CBMS) and services in networked
      systems,   except   for   certain    single-processor    systems.
      Specifically,  the  standard  does not apply to a CBMS if it is a
      stand-alone system which is not  interconnected  with  any  other
      CBMS:  nevertheless, conformance with the standard is recommended
      under these circumstances particularly if there is a  possibility
      that  use  of another central processing unit, or interconnection
      with another system, will be required in the future.  Where a new
      CBMS node is incorporated into an existing network, the  standard
      applies  at  the  interface  between  CBMS's.  In  this instance,
      previously existing nodes may  accommodate  the  standard  either
      through  retrofit  or  by  the use of a translator.  In addition,
      networks  that  are  established  strictly  for  the  purpose  of
      supporting  research  in  computer  science or communications are
      exempt from complying with this standard.

      Subcommittee TC97/SC16  of  the  International  Organization  for
      Standardization   (ISO)  has  developed  a  reference  model  for
      describing communications between "open" systems.  (ISO/TC97/SC16
      DIS7498) This model is known as the ISO Reference Model for  Open
      Systems   Interconnection   (OSI).    It  divides  communications
      protocols   into   seven   layers,    ranging    from    physical
      interconnection   at   the  lowest  layer  to  data  exchange  by
      applications programs at the top.

      The NBS message format deals with data  used  by  an  application
      within  a  system; it is not a protocol.  Messages defined by the

                                      2

      NBS   message   format   would   be  manipulated  by  a  layer  7
      (Application) protocol.

      A message as referenced by the NBS message format is  a  unit  of
      communication from an originator to a recipient, exclusive of any
      message  heading  or  control information (often referred to as a
      message envelope).  An originator  and  recipient  are  typically
      people  but  may  be  roles  or  processes.   A role identifies a
      function within an organization as opposed to an  individual  who
      performs  that  function.  A process refers to a computer process
      that might originate or receive a message.

      Special Information. Certain characteristics distinguish  a  CBMS
      from  other  systems  for  sending  messages.    Originators  and
      recipients  may  be  terminal  users   or   processes   (discrete
      software).    A  system  in  which  the  originator  addresses  a
      particular terminal device rather than a particular recipient  is
      not  considered to be a CBMS.  The recipient's system need not be
      available when the originator sends a message.  The  message  can
      be  stored  in the originator's system or at an intermediate node
      in the network until the recipient's  system  becomes  available.
      In  addition,  a  CBMS  offers  both message creation and message
      processing facilities as part of the system.  A CBMS offers  text
      editing  facilities  to  assist  the user in the preparation of a
      message.   The  recipient  CBMS  stores  the  message  until  the
      recipient  chooses  to  read  it.    Message systems which do not
      provide these minimum functions are not considered CBMS's.

      The intent of the message format standard is to  allow  users  of
      different computer based message systems to send messages to each
      other.    The  standard  does  not  make  demands  on the message
      transfer system except that it transports messages transparently.
      The standard makes some simple demands on the  CBMS.    The  CBMS
      must  recognize  fields  within  the  message,  process fields in
      predetermined ways, create messages  in  the  correct  form,  and
      recognize  and  create  data  elements of messages in the correct
      format.  The standard does not dictate or constrain the  services
      that  the  CBMS  provides for users, or the way that messages are
      stored, represented, manipulated, or presented to the user by the
      CBMS.

      The standard does constrain the format  of  the  message  at  the
      interface  between  systems.   This guarantees that, whatever the
      source of the message, it arrives at the receiving system in  the
      standard   format.      The  message  format  standard  separates
      information into fields so that the CBMS can locate  and  operate
      on  that  information.   The message is converted from the format
      used within the originator's CBMS  to  the  standard  format  (if
      different)  on  leaving  the  originator's  CBMS.  The message is
      converted from the standard format to the format used within  the
      recipient's CBMS (if different) on entering the recipient's CBMS.

                                      3

      Specifications.  Federal  Information Processing Standard (FIPS),
      Message Format for Computer Based Message Systems (affixed).

      Qualifications. None

      Implementation Schedule. All  applicable  equipment  or  services
      ordered  on  or after 24 months from the date of issuance of this
      FIPS PUB, and all CBMS development initiated inhouse on or  after
      12  months  from the date of issuance of this FIPS PUB must be in
      conformance with this standard unless a waiver has been  obtained
      in  accordance  with the procedure described below.  An exception
      to this standard is made when procurement actions  are  into  the
      solicitation phase on the date of issuance of this FIPS PUB.

      Waivers.  Heads  of agencies may request that the requirements of
      this standard be waived in instances  where  it  can  be  clearly
      demonstrated  that  there  are  appreciable  performance  or cost
      advantages to be gained and that the  overall  interests  of  the
      Federal  Government  are  best  served  by granting the requested
      waiver.  Such waiver requests will be reviewed by and are subject
      to the approval of the Secretary of Commerce.  The waiver request
      must address the criteria stated above as the  justification  for
      the waiver.

      Forty-five  days should be allowed for review and response by the
      Secretary of Commerce.  Waiver requests shall be submitted to the
      Secretary of Commerce, Washington, D.C. 20230, and labeled  as  a
      Request   for  a  Waiver  to  a  Federal  Information  Processing
      Standard.  No agency shall take any action to  deviate  from  the
      standard  prior  to  the  receipt  of  a waiver approval from the
      Secretary of Commerce.  No agency  shall  begin  any  process  of
      implementation  or acquisition of non-conforming equipment unless
      it has already obtained such approval.

      Where to Obtain Copies. Either paper or microfiche copies of this
      Federal  Information  Processing  Standard,  including  technical
      specifications,  may  be  purchased  from  the National Technical
      Information  Service  (NTIS)  by  ordering  Federal   Information
      Processing Standard Publication (FIPS-PUB-98), Message Format for
      Computer  Based Message Systems.  Ordering information, including
      prices and delivery alternatives, may be obtained  by  contacting
      the   National   Technical   Information  Service  (NTIS),  U. S.
      Department of Commerce, Springfield,  Virginia  22161,  telephone
      number  (703)  487-4650.    Payment  may  be made by check, money
      order, purchase order, credit card, or deposit account.

                                      4

                                                      Executive Summary

                              EXECUTIVE SUMMARY

           The  message  format  specification addresses the problem of
      exchanging  messages  between  different  computer-based  message
      systems  (CBMSs).    This interchange problem can be addressed on
      several  levels.    One  level  specifies  the  physical   inter-
      connections,  another  specifies  how information travels between
      CBMSs, another specifies  form  and  meaning  of  messages  being
      interchanged.    The  highest  level  specifies  operations  on a
      message.  Each of these levels would be covered  by  a  different
      standard.

           This  message format specification addresses only the issues
      of form and meaning of messages at the points in time  when  they
      are  sent  from  one  CBMS and received by another.  Messages are
      composed of fields, containing different classes of  information.
      These  fields  contain  information about the message originator,
      message recipient, subject matter, precedence and  security,  and
      references  to  previous  messages,  as  well  as the text of the
      message.  Standard formats (syntax) for messages provide a  basis
      for  the  contents  of  messages  generated  by  one  CBMS  to be
      processed by another CBMS.  Standard meanings (semantics) for the
      components of a message facilitate standard interpretation  of  a
      message,  so  that  everyone receiving a message gets the meaning
      intended by its sender.

           Each CBMS that implements this message format  specification
      will  be  compatible  with  any  other  CBMS  that implements the
      specification, provided that the use of optional fields and  data
      elements  is  negotiated  in  advance.    This  ensures  that the
      contents of a message posted by one  CBMS  can  be  received  and
      interpreted by a different CBMS.

           This  message  format  specification has been developed as a
      result of examining CBMSs currently  in  use  in  commercial  and
      research  environments.    Three major design perspectives helped
      shape the message format specification.

        o  Viability.    The  message  format  specification   uses
           concepts  that  already work.  It has been designed with
           implementation concerns in mind.

        o  Compatibility.    The   message   format   specification
           contains concepts from existing CBMSs.  For this reason,
           many CBMS would already contain functions and components
           similar  to  those  required  to  implement  the message
           format specification.

                                      5

                                                      Executive Summary

        o  Extensibility.      This  message  format  specification
           defines a broad range of message content components  and
           requires  only an elementary subset of them.  This means
           that even a very simple CBMS can implement  the  message
           format  specification.  The message format specification
           contains a rich  set  of  optional  components  and,  in
           addition,  mechanisms  for  user  extensions  and future
           extensions to the message format specification.

           The  message  format  specification  defines  the  form  and
      meaning  of  message  contents  and their components as they pass
      from one CBMS to another through a message transfer system.   The
      message   format  specification  does  not  address  any  of  the
      following major issues.

        o  Functions or services provided to a user by a CBMS.
                For  example,  the  message  format   specification
                assumes  that  every CBMS allows a user to send and
                receive messages.  It does not specify any  of  the
                details of how a send function or a message-reading
                function  might  work or how it might appear to the
                user.  That is, the  message  format  specification
                neither limits nor mandates functions.

        o  Storage or format of message contents in a CBMS.
                The  message  format specification defines the form
                and contents of messages when they are  transferred
                between  systems.   A CBMS may or may not choose to
                use the same format for internal storage.

        o  Message transfer system protocols.
                The message format specification does  not  specify
                how  a  message  travels  between  CBMSs.   It does
                specify the form of its contents as it  leaves  and
                arrives,  assuming  only  that the message is moved
                transparently by the transfer system.

        o  Message envelopes.
                While a message is traveling between CBMSs,  it  is
                enclosed  in a message envelope.  Message envelopes
                contain all the information about a message that  a
                message transfer system needs to know.  The message
                format  specification does not define the format or
                content of a message envelope.

        o  How message originators and recipients are identified.
                The message format specification does not provide a
                representation scheme for the names or addresses of
                message originators  and  recipients  as  they  are
                known to a CBMS.

                                      6

                                                              Section 1

      1.  INTRODUCTION

           A  computer-based message system (CBMS) allows communication
      between "entities" (usually people) using computers.    Computers
      serve  both  to mediate the actual communications between systems
      and to provide users with facilities for creating and reading the
      messages.

           CBMSs have  been  developing  for  over  ten  years.    More
      recently,  CBMSs  have  been one of the bases in industry for the
      introduction of office automation.  A growing number  of  organi-
      zations  use  either  their own or a commercially available CBMS.
      The design and complexity of these systems  vary  widely.    This
      message  format  specification  provides  a basis for interaction
      between different CBMSs by defining the format of messages passed
      between them.

      1.1  Guide to Reading This Document

           The method of presenting the material in this  specification
      is  to  combine  the technical specification with tutorial infor-
      mation.  This approach has been taken to place the  specification
      in context and improve its readability.

           The  core of the technical information in the document is in
      Section 2, "A Simple Model of a CBMS Environment";  Section  3.1,
      "Semantics  of  Message Fields"; Section 4.2, "Overview of Syntax
      Encoding"; and Section 4.3, "Data Element Syntax".  Appendixes  A
      and  B  consolidate  the technical information.  These appendices
      are designed  for  ease  of  reference  and  should  be  read  in
      conjunction   with   the  body  of  the  report  for  a  complete
      understanding of the message format  presented  in  the  specifi-
      cation.

           Section  2  presents  a simple model of operation of a CBMS.
      Section 3 discusses the components of messages and their  meaning
      (semantics),    including    discussions   of   the   recommended
      relationship between message components and CBMS user  functions.
      (See  Section  3.2.)    Section  4  presents  details of the form
      (syntax) required for components of a message.

           Appendix D summarizes the components of  messages  according
      to  whether  they are required or optional for CBMSs implementing
      the message format  specification.    Appendix  E  organizes  the
      message  components  according  to  the  functional  class of the
      components.  Appendix F provides an  overview  of  the  syntactic
      elements defined by this message format specification; Appendix G

                                      7

                                                            Section 1.1

      summarizes  those elements according to whether they are required
      or optional for a CBMS implementing the message  format  specifi-
      cation.  Examples of each syntactic element appear in Appendix H,
      displaying syntax and describing the associated semantics.

      1.2  Vendor-Defined Extensions to the Specification

           This  specification provides the capability of extending the
      range of functionality by the use  of  vendor-defined  qualifiers
      and  vendor-defined  data  elements.    Any  vendor who uses this
      capability to provide services which are  essentially  equivalent
      to  those already designated as required, basic, or optional does
      not comply with the specification.

      1.3  The Scope of the Message Format Specification

           The purpose of  this  message  format  specification  is  to
      present  the  semantics  and syntax to be used for messages being
      exchanged between CBMSs.  Specifically, it defines the following:

        o  The meaning and form of standard fields to  be  used  in
           messages.

        o  Which fields must be present in all messages.

        o  Which fields complying CBMSs must be able to process.

        o  How  messages,  fields, and the data contained in fields
           are represented.

      1.4  Issues Not Within the Scope of the Message Format Specifi-
           cation

           The  message  format  specification  does  not  address  the
      following  issues,  some  of which are being covered by other NBS
      standards development programs  at  the  Institute  for  Computer
      Sciences and Technology (ICST).  (See [BlaR-80] for a description
      of the ICST network protocols program.)

        o  The nature of a message transfer system, except to state
           the assumption that it transfers messages transparently.

                                      8

                                                            Section 1.4

        o  The  form  or  nature  of the protocols used to transfer
           messages (posting, relay, and delivery protocols).

        o  The content and representation of message envelopes.

        o  Representations for unique identifiers  (in  particular,
           message identifiers).

        o  Network and internetwork addressing.

        o  Representations  for  identities  of message originators
           and recipients.

        o  Certain message processing functions that CBMSs  provide
           for  users,  e.g., those concerned with the creation and
           editing of text.

        o  Presentation of messages to users.

        o  Representations for multi-media objects.

        o  Data representation for messages within CBMSs.

        o  Data sharing or any storage management within CBMSs.

        o  Representations for fixed  or  floating  point  numbers.

      1.5  Relationship to Other Efforts

           The  message  format specification is based on several docu-
      ments and the current state  of  many  CBMSs  available  both  in
      industry and the research community.  These documents include the
      standardization efforts in the ARPANet [CroD-77, PosJ-79] and the
      CCITT,  proposed  ISO  and  ANSI  header  format standards [TasG-
      80, ISOD-79], the work of IFIPS Working Group  6.5,  and  various
      papers  about the general nature of mail systems, addressing, and
      mail delivery.  (See [FeiE-79] for references.

                                      9

                                                              Section 2

      2.  A SIMPLE MODEL OF A CBMS ENVIRONMENT

           In  order  to provide a framework for presenting the message
      format specification, this section describes a simple  functional
      model for a CBMS.  The model provides a high-level description of
      both  user  facilities  and  system architecture.  Discussions of
      messages, message originators, and message  recipients  serve  to
      further clarify the nature of a CBMS.

           A  CBMS permits the transfer of a message from an originator
      to a recipient.  "Originator" and "recipient" are used  in  their
      normal  English  senses.    (See Section 2.4.)  A message (in its
      most abstract definition) is simply a unit of communication  from
      an  originator  to a recipient.  A CBMS offers several classes of
      functions to its users:

        o  Message Creation:  The  facilities  used  by  a  message
           originator  to  create messages and specify to whom they
           are to be sent.

        o  Message Transfer: The facilities used to convey  a  mes-
           sage to its recipient(s).

        o  Recipient  Processing:  The facilities used by a message
           recipient to process messages that have arrived.

           These classes of functions are presented in more  detail  in
      Section 3.2.

           CBMSs  differ  from  other  office automation/communications
      systems in a number of ways.

        o  Unlike other types of  electronic  communications,  CBMS
           messages  are  sent  to  particular  individuals, not to
           stations or telephone sets.  If a recipient moves  to  a
           different  location, messages sent to that recipient are
           delivered to the recipient at the new location.

        o  Transmission of CBMS  messages  is  asynchronous.    The
           recipient's  system  need not be available when the mes-
           sage leaves the originator's  system.    That  is,  CBMS
           message transfer facilities are store-and-forward.

        o  CBMS  messages can contain a wide variety of data.  They
           are not constrained to any single kind of communication.
           CBMS messages are often simple  memoranda  but  are  not
           restricted to text.  A CBMS message may contain any kind

                                     10

                                                              Section 2

           of  data  that  an originator wishes to send to a recip-
           ient.  By contrast, Teletex  systems  and  communicating
           word  processors  handle  the  transfer  of  final  form
           documents; compatible communicating word processors  can
           exchange  documents in editable form; Telex and TWX deal
           in unformatted text.

        o  CBMSs offer message creation facilities as an  important
           part  of  the  system.  CBMSs assist users in the prepa-
           ration of messages by  having  text  editing  facilities
           available  and allowing users to include data stored on-
           line in messages.  Some CBMSs also  interface  to  other
           office  automation  facilities,  such  as formatters and
           spelling correctors.  This is not true of Telex, TWX, or
           similar services.

        o  CBMSs offer recipient processing facilities as an impor-
           tant part of the system.  This is not true of most other
           forms of electronic communications.  For example,  Telex
           and TWX systems simply print messages on paper when they
           are  received,  without  retaining a copy in the system.
           (Teletex systems are similar to Telex systems, but  some
           can  retain  a  copy  of the document in local storage.)
           Communicating  word  processors   might   notify   their
           operators  that  a  document  has  been  received and is
           stored on-line, but they offer  little  in  the  way  of
           other recipient processing facilities.  Most CBMSs offer
           at least the following recipient processing facilities:

             .  The  ability  to retain a copy of a message on-line
                after it has been read.

             .  The ability to examine or  delete  stored  messages
                individually.

             .  The ability to organize messages using some form of
                electronic "file folder."

             .  The  ability  to  determine  if a message is recent
                (has arrived since the last time the recipient used
                the CBMS) or unseen (has never been examined by the
                recipient).

             .  The  ability  to  summarize  stored  messages.    A
                summary   usually   includes  information  such  as
                whether the message is recent or  unseen,  when  it
                was  received,  its length, who it is from, and its
                subject.

             .  The ability to retrieve a stored message based upon

                                     11

                                                              Section 2

                one  or  more of its attributves (for example, when
                the message was received, whether  or  not  it  has
                been  seen  or deleted, and the values contained in
                its fields).

             .  A forward facility that allows users to include all
                or part of a message in a new outgoing message.

             .  A reply facility that allows users to  answer  mes-
                sages  without having to enter a new list of recip-
                ients.

      2.1  Logical Model of a CBMS

           CBMS facilities for message creation, transfer,  and  recip-
      ient  processing  are  reflected  in  a  logical  model of a CBMS
      developed by IFIP Working Group 6.5.  (An  essentially  identical
      model  is  being  used  by  CCITT  Study  Group  VII, Question 5,
      regarding  Message  Handling  Systems [CCIT-82].)     The   model
      consists  of  a  Message  Transfer  System  and  a number of User
      Agents.  (See Figure 1.)

                    |                  |
                    |     *************     |
      *********  ------>  *  Message  *  ------->  *********
      * User  *  Posting  * Transfer  *  Delivery  * User  *
      * Agent *  Protocol *  System   *  Protocol  * Agent *
      *********  <------- *************  <-------  *********
                    |                       |
                    |                       |
                 Posting                Delivery
                  Slot                    Slot

                          Message Flow
      Originator --------------------------------> Recipient

      FIG. 1.  LOGICAL MODEL OF A COMPUTER-BASED MESSAGE SYSTEM

           A User Agent (UA) is a functional entity that acts on behalf
      of a user, assisting with creating and  processing  messages  and
      communicating with the Message Transfer System.

           The Message Transfer System(MTS) is an entity that accepts a

                                     12

                                                            Section 2.1

      message from its originator's User Agent and ultimately passes it
      to  each  of  its  recipients' User Agents.  The Message Transfer
      System may perform routing and storage functions  (among  others)
      in order to accomplish its task.

           Transferring  a  message  from an originator's User Agent to
      the Message Transfer System is called Posting;  the  originator's
      User  Agent  and  Message  Transfer  System  engage  in a Posting
      Protocol in order to accomplish Posting.  Transferring a  message
      from  the  Message Transfer System to a recipient's User Agent is
      called Delivery; the recipient's User Agent and Message  Transfer
      System  engage  in  a  Delivery  Protocol  in order to accomplish
      Delivery.

           The point at which responsibility for a  message  is  trans-
      ferred  is called a Slot.  The Posting Slot is the point at which
      responsibility for a message passes  from  an  originator's  User
      Agent  to  the  Message Transfer System; the Delivery Slot is the
      point at which responsibility  for  a  message  passes  from  the
      Message Transfer System to a recipient's User Agent.

           The  model  divides  messages  into  two  parts, the message
      content and the message envelope.  The  message  content  is  the
      information  that the originator wishes to send to the recipient;
      this message format specification deals solely with  the  message
      content.    The  message envelope consists of all the information
      necessary for the Message Transfer System to  do  its  job;  this
      message   format  specification  does  not  specify  the  message
      envelope.  Some of the data appearing  on  the  message  envelope
      could  be  redundant with some data found in the message content.
      The Message Transfer  System  is  not  expected  to  examine  the
      message content unless it is told to do so by the originator's or
      recipient's User Agent.

           This  message format specification places no restrictions on
      the Message Transfer System itself, except that  it  be  able  to
      transfer  messages  between originating and receiving UAs without
      reading or altering the contents  of  messages  unless  otherwise
      instructed by the UAs.  In addition, this message format specifi-
      cation  does  not dictate the form or nature of any protocol used
      by the Message Transfer System.   Finally,  this  message  format
      specification does not specify the content or form of the message
      envelope.   That is, the message format specification defines the
      format for the contents of messages, not the manner in which they
      are transmitted.

           Many of today's commercially available CBMSs incorporate all
      of the facilities  represented  in  the  logical  model.    Their
      architectures  may  reflect  the economies that can be taken when
      implementing systems  that  are  self-contained.    For  example,
      stand-alone  systems  that  store  messages  in  a single central

                                     13

                                                            Section 2.1

      database  require  no  Message Transfer System; an implementation
      may integrate software for User Agent and Message Transfer System
      functions, doing away with Posting or Delivery Protocols.

      2.2  Relationship to the ISO Reference Model for Open Systems
           Interconnection

           Subcommittee TC97/SC16 of the International Organization for
      Standardization  (ISO)  has  developed  a  reference  model   for
      describing communications between "open" systems [ISOD-82].  This
      model  is  known  as  the  ISO  Reference  Model for Open Systems
      Interconnection (OSI).  It divides communications protocols  into
      seven layers, ranging from physical interconnection at the lowest
      layer to data exchange by application programs at the top.

           This message format specification deals with data used by an
      application  within  a  system.    Thus, the message format being
      specified here is not a protocol.  Since it is not a protocol, it
      lies outside of the model for open systems interconnection.  User
      Agents are application layer entities (layer 7), however, and the
      protocols used by a message transfer system are above the session
      layer (layer 5).

      2.3  Messages and Fields

           A message is a unit of communication from an originator to a
      recipient.  A message consists of a series of  components  called
      fields.   Fields can be described according to their meaning in a
      message (semantics) and according to the format required for them
      in a message (syntax).

           Semantically, a field is just a component of a message;  the
      meanings  of particular fields are defined by this message format
      specification.  Syntactically, a field is a unit  of  data  whose
      form is defined by this message format specification.  Additional
      fields can be defined by users or vendors as long as they conform
      to  the  syntactic  and  semantic  rules that this message format
      specification defines for additional fields.

           (A note on terminology: A  message  consists  of  components
      called  fields.  The words "message" and "field" are used both in
      the informal sense  of  the  previous  sentence  and  in  a  more
      restricted  sense  as names of particular syntactic elements.  As
      syntactic  element  names,   Message   and   Field   are   always
      capitalized.)

                                     14

                                                            Section 2.3

           Some  CBMS functions are based on the contents of particular
      fields; other functions (such as the ability to read  a  message)
      may  have  little  to do with the fields themselves.  Section 3.2
      discusses some of  the  specific  functions  that  a  CBMS  might
      provide  to  users  and  the  fields that must be used to support
      those functions.

      2.4  Message Originators and Recipients

           This message format specification refers to  message  origi-
      nators  and recipients.  These terms were defined functionally in
      Figure 1.  When the message format specification  refers  to  the
      identity  of  a  message  originator or recipient, it means "that
      information which uniquely identifies the message  originator  or
      recipient  within  the  domain of the given message system."  The
      syntax and semantics of message addressing  are  not  within  the
      scope of the message format specification.

           Originators  and  recipients can be people, roles, processes
      or groups.

           People.  People as originators and recipients  are  specific
      individuals.

           Roles.    Roles  identify  functions within organizations as
      opposed to the  specific  individuals  who  perform  them.    For
      example,  consider  a  newspaper  that  produces both morning and
      evening editions and therefore operates with more than one shift.
      Someone wishing to contact the city desk would send a message  to
      the  city  desk  role rather than trying to determine exactly who
      was assigned to the city desk at a specific time.    (Of  course,
      messages  can usually be sent to the individuals directly whether
      or not they are actually performing a role at the time.)

           Processes.  A process in a computer could serve as either an
      originator or a recipient for messages.  A computer system  might
      originate  a  message  to  notify a recipient about the status of
      some task.  For example, an archive utility  could  notify  users
      about  files  that  have been archived; a distributed file system
      could notify a user that a remote file has been  deposited  on  a
      local file system.  Messages could be used by computer systems to
      warn  about  some  impending  condition  or  even  to monitor the
      performance of the computer itself.  Some computer processes  may
      also  be  message  recipients,  taking  action based upon message
      contents.

           In addition, some CBMSs allow messages to be sent to groups.
      A group is a predefined list of  message  recipients.    Using  a

                                     15

                                                            Section 2.4

      group   name  as  a  recipient  permits  message  originators  to
      designate a potentially large number of recipients using a single
      recipient identifier.  This makes using the CBMS more  convenient
      and accurate.

                                     16

                                                              Section 3

      3.  SEMANTICS

           This  section discusses two major topics, message processing
      functions and message field meanings.  Section 3.1 describes  the
      six  functional  groups of message fields.  The functional groups
      are Origination, Dates, Recipients,  Cross-referencing,  Message-
      handling, and Message-contents.  They are explained more fully in
      Section 3.1.1, along with detailed discussion of the semantics of
      all  the  fields in each functional group.  Section 3.2 describes
      message processing functions whose  operation  is  based  on  the
      meanings of particular message fields.

      3.1  Semantics of Message Fields

           The  definition  of  a  message  is  discussed  generally in
      Sections 1 and 2.  Semantically valid messages must  contain  one
      From  field,  one  To field, and one Posted-Date field.  They may
      contain, in addition, any number of other  fields,  depending  on
      the  processing  and  functions  supplied  by  the originating or
      receiving CBMS.  (Section  3.2  describes  classes  of  functions
      supplied by CBMSs.)

      3.1.1  Types of fields

           Message  receiving programs are required to interpret fields
      according to the semantics described in  the  remainder  of  this
      section.  The message fields defined in this document are grouped
      into the following functional categories.

        o  Originator  fields  indicate who or what participated in
           the creation of the message and where replies should  be
           directed.  (See Section 3.1.3.)

        o  Date fields record when events take place, for a variety
           of events, such as message creation or expiration.  (See
           Section 3.1.5.)

        o  Recipient  fields  indicate  who  or what is intended to
           receive a message.  (See Section 3.1.4.)

        o  Cross-reference fields label a message or refer to other
           messages.  (See Section 3.1.6.)

        o  Message-handling fields record the  type  of  service  a

                                     17

                                                          Section 3.1.1

           message's  sender requested of a message transfer system
           or indicate how the message should  be  treated  by  its
           recipients.  (See Section 3.1.7.)

        o  Message-content   fields   either  contain  the  primary
           content of a message, or index the message, or summarize
           the message.  (See Section 3.1.8.)

        o  Extension fields provide mechanisms  for  extending  the
           message format specification.  (See Section 3.1.9.)

      3.1.2  Semantic Compliance Categories

           For purposes of determining whether a CBMS complies with the
      semantic  requirements of this message format specification, mes-
      sage fields have been divided into three categories:

      REQUIRED  These fields must be present in all messages  and  must
                be  processed  by message receiving programs as defined
                by the message format specification.

      BASIC     These fields need not be present in  all  messages  but
                when  they do appear, they must be processed by message
                receiving programs as defined  by  the  message  format
                specification.

      OPTIONAL  These  fields  need  not be present in all messages and
                may be ignored by  message  receiving  programs.    The
                exact  meaning  of  "ignored"  is  not specified by the
                message format specification.   However,  a  CBMS  must
                recognize  the existence of an optional field (that is,
                optional fields should not cause errors) and  must  not
                process the field in a manner contrary to the semantics
                defined  for  that field by the message format specifi-
                cation.  It is left to the discretion of a  recipient's
                CBMS  what  action is to be taken when an instance of a
                locally unimplemented optional field is detected.

           (Syntactic compliance is defined in Section 4.1.2.)

      3.1.3  Originator fields

           A message originator may be  a  person,  role,  or  process.
      Originator fields identify a message's author, who is responsible
      for   the   message,   who   or  what  sent  it,  and  where  any
      replies should be directed.  (See Section 2.4.)

                                     18

                                                          Section 3.1.3

      From                     (REQUIRED)

                This  field  contains the identity of the originator(s)
                taking formal responsibility for  this  message.    The
                contents  of  the  From field is to be used for replies
                when no Reply-to field appears in a message.

      Reply-To                 (BASIC)

                This field identifies any recipients of replies to  the
                message.

      Author                   (OPTIONAL)

                This  field  identifies the individual(s) who wrote the
                primary contents of the message.   Use  of  the  Author
                field  is  discouraged  when the contents of the Author
                field and the From field would be completely redundant.

      Sender                   (OPTIONAL)

                This field identifies the agent who sent  the  message.
                It is used either when the sender is not the originator
                responsible  for the message or to indicate who among a
                group  of  originators  responsible  for  the   message
                actually   sent  it.    Use  of  the  Sender  field  is
                discouraged when the contents of the Sender  field  and
                From  field  would be completely redundant.  The sender
                field may specify  only  one  originator  identity  and
                appear only once in a message.

      3.1.4  Recipient fields

           Message  recipients  may  be  people,  roles,  processes, or
      groups.  (See Section 2.4).  Recipient  fields  identify  who  or
      what is to receive the message.

      To                       (REQUIRED)

                This  field  identifies  the  primary  recipients  of a
                message.

      Bcc                      (OPTIONAL)

                This  field  identifies  additional  recipients  of   a
                message  (a  "blind carbon copies" list).  The contents
                of this field are not to be included in copies  of  the
                message  sent  to the primary and secondary recipients.
                See section 3.2.1 for further discussion of the use  of
                blind carbon copies lists.

                                     19

                                                          Section 3.1.4

      Cc                       (BASIC)

                This field identifies secondary recipients of a message
                (a "carbon copies" list).

      Circulate-Next           (OPTIONAL)

                This field is used in conjunction with the Circulate-To
                field.    (See  Section  3.2.6.1.)    It identifies all
                recipients in a circulation list who have not  received
                the message.

      Circulate-To             (OPTIONAL)

                This   field  identifies  recipients  of  a  circulated
                message.   (See  Section  3.2.6.1.)    It  is  used  in
                conjunction with the Circulate-Next field.

      3.1.5  Date fields

           Date  fields  for two kinds of uses are provided.  Dates can
      be associated with some event in the history  of  a  message  and
      dates  can  delimit  the span of time during which the message is
      meaningful (its life span).

      Posted-Date              (REQUIRED)

                This field contains the  posting  date,  which  is  the
                point  in  time  when  the  message  passes through the
                posting slot into a message transfer system.  Only  one
                Posted-Date field is permitted in a message.

      Date                     (OPTIONAL)

                This   field   contains   a  date  that  the  message's
                originator wishes to associate with  a  message.    The
                Date field is to the Posted-Date field as the date on a
                letter is to the postmark added by the post office.

      End-Date                 (OPTIONAL)

                This  field  contains the date on which a message loses
                effect.  (See also Section 3.2.5.)

      Received-Date            (OPTIONAL)

                This field is also called Delivery date.    This  field
                may  be  added  to a message by the recipient's message
                receiving program.  It indicates when the message  left

                                     20

                                                          Section 3.1.5

                the delivery system and entered the recipient's message
                processing domain.

      Start-Date               (OPTIONAL)

                This  field  contains the date on which a message takes
                effect.  (See also Section 3.2.5.)

      Warning-Date             (OPTIONAL)

                This field is used either alone or in conjunction  with
                an  End-Date  field.    It  contains one or more dates.
                These dates could  be  used  by  a  message  processing
                program  as  warnings of an impending end-date or other
                event.  (See also Section 3.2.5.)

      3.1.6  Cross-reference fields

           Cross-reference fields can be used to identify a message and
      to provide cross-references to  other  messages.    (See  Section
      3.2.4.)

      In-Reply-To              (OPTIONAL)

                This  field designates previous correspondence to which
                this message is a reply.  The usual  contents  of  this
                field  would be the contents of the Message-ID field of
                the message(s) being replied to.

      Message-ID               (OPTIONAL)

                This field contains a unique identifier for a  message.
                This  identifier is intended for machine generation and
                processing.   Further  definition  appears  in  Section
                3.2.4.1.    Only one Message-ID field is permitted in a
                message.

      Obsoletes                (OPTIONAL)

                This field identifies one or more  messages  that  this
                one replaces.

      Originator-Serial-Number (OPTIONAL)

                This field contains one or more serial numbers assigned
                by  the  message's  originator.  Messages with multiple
                recipients  should  have  the   same   value   in   the
                Originator-Serial-Number field.

                                     21

                                                          Section 3.1.6

      References               (OPTIONAL)

                This  field  identifies  other correspondence that this
                message  references.    If  the  other   correspondence
                contains  a  Message-ID  field,  the  contents  of  the
                References field must be the message identifier.

      3.1.7  Message-handling fields

           Message-handling fields describe aspects of how a message is
      to be handled or categorized.

      Precedence               (OPTIONAL)

                This  field  indicates  the  precedence  at  which  the
                message  was posted.  Ordinarily, message precedence or
                priority is a service request  to  a  message  transfer
                system.    A  message  originator, however, can include
                precedence information in a message.   One  example  of
                precedence  categories  are  those  used  by  the  U.S.
                Military: "ROUTINE,"  "PRIORITY,"  "IMMEDIATE,"  "FLASH
                OVERRIDE,"  and "EMERGENCY COMMAND PRECEDENCE."

      Message-Class            (OPTIONAL)

                This  field  indicates  the  purpose of a message.  For
                example, it might contain values  indicating  that  the
                                                             1
                message is a memorandum or a data-base entry. 

      Reissue-Type             (OPTIONAL)

                This   field   is  used  in  conjunction  with  message
                encapsulating  (see  Section  3.2.2)  to  differentiate
                between messages being assigned or redistributed.

      Received-From            (OPTIONAL)

                This  field  contains  a  record  of  a  message's path
                through   a   message    transfer    system.        The
                recipient's  message receiving program could store here
                any information about the  transfer  that  it  obtained
                from a message transfer system.
      _______________

        1
         The message format specification is not intended to be used as
      a  specification  for  exchanging  data-base  records.  Messages,
      however, sometimes contain data from or for a database.

                                     22

                                                          Section 3.1.7

      3.1.8  Message-content fields

           The   intent   of  most  messages  is  to  communicate  some
      particular information from originator  to  recipient.    Several
      fields in a message are designed to contain that information.

      Subject                  (BASIC)

                This  field  contains  any  information  the originator
                provided to summarize or indicate  the  nature  of  the
                message.

      Text                     (BASIC)

                This field contains the primary content of the message.

      Attachments              (OPTIONAL)

                This  field  contains  additional  data  accompanying a
                message.  It is similar in intent to  enclosures  in  a
                conventional mail system.

      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 specifi-
                cation 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.

                                     23

                                                          Section 3.1.9

      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.)

      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 3.2.2) 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.

                                     24

                                                          Section 3.2.1

           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  a  message  (that
      is,  write, but not necessarily enter it into the CBMS); 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,  respon-
      sible  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.

           The use of the Cc field is  identical  to  current  business
      practice.  This field contains the formal secondary recipients of
      the message.

           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 other than the originator who
      are not included in the Bcc field itself.  Some  systems  include
      the  contents  of  the  Bcc  field only in the originator's copy;
      others include all or part of the Bcc field in the copies sent to
      the recipients indicated in the Bcc field.    This  specification
      does not indicate exactly how the Bcc field is to be treated.

      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.  Making others aware of the complete and
           unaltered contents of the message.

                                     25

                                                          Section 3.2.2

        o  Assignment.  Delegating 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
      supporting  reissuing.  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.

           This  procedure for passing on previously sent messages is a
      matter of organizational policy  and  has  authentication  as  an
      associated  issue.   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.)

      _______________

        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.

                                     26

                                                        Section 3.2.2.2

                            The Original Message
      John Doe wishes Jane Jones to get a copy of the following
      message:
                      Message:
                        Field: From "Jean Smith"
                        Field: Posted-Date "27 January 1983"
                        Field: To "John Doe"
                        Field: Subject "Next Project Meeting"
                        Field: Text "The agenda for ..."

                               Redistribution
      Message:
        Field: From "John Doe"                  John Doe is responsible
        Field: Posted-Date "28 January 1983"    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 "27 January 1983"
          Field: To "John Doe"
          Field: Subject "Next Project Meeting"
          Field: Text "The agenda for ..."

                                 Forwarding
      Message:
        Field: From "John Doe"
        Field: Posted-Date "28 January 1983"
        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 27 January 1983              Note that John's CBMS
           Subject Next Project Meeting         has chosen to represent
                                                it as a text string.
           The agenda for ..."

      FIG. 2.  MESSAGE FORWARDING AND REDISTRIBUTION

                                     27

                                                        Section 3.2.2.2

      3.2.2.2  Assignment

           Assignment is the process of designating responsibility.  In
      some  organizations, formal message traffic is distributed to 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.

      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 recip-
      ients of a reply.

           A Reply-To field is defined by this message format  specifi-
      cation.    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:

        o  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.

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

        o  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.

                                     28

                                                          Section 3.2.3

           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 offer additional reply facil-
      ities, depending on their view of users' organizational  require-
      ments.

      3.2.4  Cross-referencing

           A  CBMS  message  may  include  designator(s) which identify
      other message(s).  The designators are used to refer  to  related
      messages so that all information in a chain of correspondence can
      be  determined  by  a CBMS user.  The designator used to identify
      and cross-reference messages can take either of two forms, unique
      identifiers or serial numbers.

      3.2.4.1  Unique identifiers

           Unique identifiers are machine-generated  and  are  intended
      primarily  for  processing  by  computers.    While they could be
      examined by a human user, unique identifiers are not  necessarily
      useful or convenient for people.

           Unique  identifiers  occur  in  several  contexts.  They are
      often used  to  identify  the  contents  of  idual  messages
      unambiguously.    When unique identifiers are used this way, they
      are called message identifiers.  Different versions of a  message
      receive  new message identifiers; an example of this is reissuing
      a message with comments.

           When a CBMS generates a message identifier, it must be  able
      to  guarantee  that  it  is unique, both within the domain of the
      individual CBMS and globally, across all connected CBMSs.   CBMSs
      could  generate  globally unique identifiers in several ways, all
      of which require prior  agreement  on  behalf  of  the  connected
      CBMSs.    One  method  is  to assign each connected CBMS a unique
      code.  A CBMS then generates unique identifiers by using its code
      as a prefix to some other value  that  it  can  guarantee  to  be
      unique  within its domain.  (This second value could be a counter
      or a timestamp/user-id combination.)

           A CBMS can provide functions for tracing  chains  of  corre-
      spondence  by  using  unique  identifiers.    The  message format
      specification defines fields for which  a  CBMS  provides  unique
      identifiers   as   values.    They  are  Message-ID,  References,
      Obsoletes, and In-Reply-To.  (See Section 3.1.6.)

                                     29

                                                        Section 3.2.4.1

      3.2.4.2  Serial numbering

           Serial  numbers  are  for  users to maintain a personal num-
      bering system for messages.  The numbers  are  composed  of  both
      letters  and  digits so that users could maintain several sets of
      sequences concurrently (for example, A1, A2, A3...  and  B1,  B2,
      B3...).

           Serial  numbers  are  assigned  at  a  defined  point in the
      history of a message.  Serial numbers are not unique identifiers;
      they differ from unique identifiers in that they are  not  neces-
      sarily generated or processed by a CBMS.  They are designed to be
      entered and read by CBMS users.  They can be as simple or complex
      as  the user requires.  Serial numbers are intended to be used to
      designate messages about a specific topic, or  messages  a  given
      user  has  sent.    Serial numbers are intended to be a permanent
      part of the message, just as unique identifiers are.

           A CBMS can provide functions  allowing  originators  to  add
      serial  numbers  to  messages.    Originator-Serial-Number is the
      field provided for an originator to add  a  serial  number  to  a
      message before sending it.

      3.2.5  Life span functions

           Messages  have life spans, usually delimited by the creation
      date and the time when the last copy of the message is destroyed.
      Messages could be meaningless before a certain time or irrelevant
      after a certain time.   For  example,  a  reminder  to  attend  a
      meeting  on  5  June  loses  most  of  its  value on the sixth; a
      reminder to attend that same meeting may be of little  use  on  5
      May (although not for the same reason).

           A CBMS can define a message's life span explicitly using the
      Start-Date  and  End-Date  fields.   A third field, Warning-Date,
      when used in conjunction with the End-Date, may be used to signal
      the approach of the End-Date.  Warning-Date may also stand  alone
      and be used by a periodic warning (alarm clock) mechanism.

           A  CBMS  could  use  these fields to help users manage their
      message stores.  For example, a message whose start date has  not
      yet  passed  could  be bypassed by a retrieval command unless the
      user requested such messages explicitly.  A CBMS  could  use  the
      end  date  to  help  with  message  store  housekeeping either by
      archiving or deleting the expired messages  automatically  or  by
      asking the user for some action to be taken on them.  The warning
      date  could  be  used  to  remind  the  user  automatically of an
      impending end date, such as a meeting reminder.

                                     30

                                                          Section 3.2.6

      3.2.6  Requests for recipient processing

           Recipients  have  a  wide variety of needs for examining and
      processing a message,  ranging  from  automatic  output  on  some
      specified  device  to  the execution of a program embedded in the
      message  itself.    Because  many  of  these  needs  are   highly
      specialized,  and  support  for them not widely implemented, this
      message format specification does not constrain the requests  for
      processing that may be included in a message.

           The  message  format  specification  does provide two fields
      that permit an originator to request circulation list  processing
      from the recipient.  These fields are Circulate-To and Circulate-
      Next.

      3.2.6.1  Message circulation

           Message  circulation  involves serial distribution of a mes-
      sage to its recipients, based on a distribution list that is part
      of the message.  The message is  delivered  first  to  the  first
      recipient  on  the distribution list.  This recipient, or someone
      the recipient delegates, sends  the  message  on  to  the  second
      recipient  on  the list, perhaps after commenting on or adding to
      the  message.    This  continues  until  all  recipients  on  the
      distribution list have received the message.

           This  message  format  specification  provides two fields to
      support message circulation.  The Circulate-To field contains the
      complete distribution list, indicating the  full  set  of  recip-
      ients,  and  the  Circulate-Next field indicates which recipients
      have not seen the message.   See  Figure  3  for  an  example  of
      message circulation using these two fields.

      3.3  Multiple Occurrences and Ordering of Fields

           Most  message  fields may occur more than once in a message;
      the  exceptions  are  the  Posted-Date,  Sender,  and  Message-ID
      fields, which may occur once, at most.  What this means is that a
      received  message  may  contain  any  number  of  instances  of a
      particular field (such as the "To" field).  If a message contains
      more than one instance of a particular field, that field  "occurs
      multiply"  and  that  message  has "multiple occurrences" of that
      field.

           A particular instance of a message field is  not  superseded
      by later instances of the same field.  The To field is an example
      of this.

                                     31

                                                            Section 3.3

      -----------------------------------------------------------------

           A  message  originator wishes to circulate a message to
           recipients A, B  and  C. The  originator  includes  the
           following fields in the message:

                     To:              A
                     Circulate-To:    A, B, C
                     Circulate-Next:  B, C

           When  recipient  A  or  someone  A delegates causes the
           message to be further circulated, the message  is  sent
           to  the  first address in the Circulate-Next field, and
           that name is removed from that field:

                     To:              B
                     Circulate-To:    A, B, C
                     Circulate-Next:  C

           B now sends the message on to its final recipient:

                     To:              C
                     Circulate-To:    A, B, C

      FIG. 3.  EXAMPLE OF MESSAGE CIRCULATION

      -----------------------------------------------------------------

           Multiple occurrences of a field are not  necessarily  equiv-
      alent  to  a single field containing the concatenated contents of
      the several instances of the given field.  For example, with  the
      Text field, concatenating the contents of several instances might
      lose  important  distinctions  between  the  contents.   A single
      message could be used to send three different documents, each one
      in a different Text field.  However, putting the three  documents
      into  a  single  Text  field would make it much more difficult to
      extract any individual document.

           Encapsulated  messages  are  exceptions  to   the   multiple
      occurrences  rule.   For example, the To field in an encapsulated
      message is not a multiple occurrence  of  the  To  field  in  the
      enclosing message.

           The fields found in a single message may occur in any order.
      The  order  in  which they occur does not necessarily reflect the

                                     32

                                                            Section 3.3

      order  in  which  they  were  created.  Nor does it constrain the
      order in which the  message  recipient  examines,  processes,  or
      displays them.

                                     33

                                                              Section 4

      4.  SYNTAX

           This section begins with an introduction to the concepts and
      elements  that  constitute  the  syntax for messages.  The second
      section presents an overview of the encoding scheme.   The  third
      section describes in detail the elements of the message syntax.

      4.1  Introduction

           This  specification  defines syntactic requirements for mes-
      sages when they are  passed  from  one  CBMS  to  another.    The
      specification is designed to meet the following goals.

        o  Provide a concise, flexible representation scheme.

        o  Simplify message parsing.

        o  Support non-textual components in messages (for example,
                                         3
           facsimile, graphics, or speech ).

      4.1.1  Message structure

           Messages   have   two  classes  of  components,  fields  and
      messages.  A field corresponds to one of the semantic  components
      defined  in  this  message  format  specification.   A message is
      simply another message.

           The type of a field in a message determines both its meaning
      and the form for its contents.  (See Section 4.3.2.)

           Fields in a  message  are  composed  of  syntactic  elements
      called  data  elements.    A  Message  data  element  is  used to
      represent messages; a Field data element  is  used  to  represent
      fields.    (The  term  "field"  is  simply  a semantic construct,
      distinct  from  "Field  Data  Element,"  which  is  a   syntactic

      _______________

        3
         While  this message format specification is not intended to be
      used as a basis for the interchange of all facsimile information,
      it does  recognize  that  CBMS  messages  may  contain  facsimile
      components.

                                     34

                                                          Section 4.1.1

      construct.)    Many  of the fields defined in this message format
      specification are restricted to containing only one kind of  data
      element.  (See Section 4.3.2.)

           Each  field defined in this message format specification has
      been assigned  a  unique  numeric  identifier  that  is  used  in
      conjunction  with  the  Field data element.  Separate identifiers
      are provided for vendor-defined  fields  and  for  extending  the
      identifier  encoding  space.    A  list of fields and identifiers
      appears in Section 4.3.2 and in Appendix C.

           Throughout the  message  format  specification,  fields  are
      referred  to  by  label name rather than by their numeric identi-
      fiers.  Field labels are names like "Sender," "Warning-Date,"  or
      "Circulate-To."    The  field labels chosen for the specification
      are names  that  are  in  common  use  in  current  CBMSs.    The
      specification  does  not require a CBMS to use these field labels
      in displaying fields to the user.  

      4.1.2  Data elements

           For the purpose of determining compliance  with  the  syntax
      defined in this specification, data elements are divided into two
      groups:

      BASIC     All   message  receiving  systems  must  process  these
                syntactic elements, interpreting their values according
                to the message format specification.

      OPTIONAL  Message  receiving  systems  need  not  process   these
                syntactic elements in order to be in compliance.

           In   addition,   complying   CBMSs  must  meet  requirements
      regarding their ability to process the  components  found  inside
      data  elements.    These  requirements  are  discussed in Section
      4.2.2.

           This message format specification  classifies  data  element
      types  as  either  primitives  or  constructors.   Primitive data
      elements,  such  as  ASCII-String,  are  basic  building  blocks.
      Constructor  data  elements, such as Message or Sequence, contain
      one or  more  primitive  or  constructor  data  elements.    Some
      constructors, such as Sequence, may be composed of any other data
      element.    Some,  such as Message, may contain only certain data
      elements. Two data elements, Extension and Vendor-Defined, may be
      classified as either primitives or constructors, depending on how
      they  are  used  to  extend  this  specification.    The  general
      syntactic form for data elements is discussed in section 4.3.1.

                                     35

                                                          Section 4.1.2

      4.1.2.1  Primitive data elements

           A   primitive   data   element  contains  a  basic  item  of
      information; it is not composed  of  other  data  elements.    In
      current  CBMSs,  the most commonly used primitive data element is
                                                 4
      ASCII-String, a series of ASCII characters.  Other primitive data
      elements are Integer,  2's  complement  integers;  Bit-String,  a
      series of bits; and Boolean, either True or False.

           One primitive data element, End-Of-Constructor, is used only
      as  a structural element within constructor data elements and has
      no meaning by itself.  End-of-Constructor is used to  provide  an
      end  marker  for  constructor  data  elements that do not have an
      explicit length; any other use is not valid syntactically.

      4.1.2.2  Constructor data elements

           The Data  Element  Contents  of  constructor  data  elements
      contain  one  or  more data elements.  The most general form of a
      constructor is a Sequence or a Set, since both Sequences and Sets
      may contain any data element.  Other constructors are specialized
      forms of sequences.

           A Message data element is a constructor.    It  may  contain
      only  Field  data  elements,  other  Message  data  elements,  or
      encrypted or data compressed forms of these elements.    A  Field
      data  element  can  contain  any data element.  It also indicates
      which specific field is being represented.  The contents of  some
      fields  are  restricted to a single type of data element, such as
      ASCII-String or Date.

      4.1.3  Properties

           Any data element may have associated  with  it  a  Property-
      List, which contains properties such as a Printing-Name or one or
      more  Comments.    Comment  A mechanism to support vendor-defined
      properties has been supplied by this specification, as well as  a
      mechanism to extend the list of property identifiers.

      _______________

        4
         An  ASCII-String  is  not limited to ASCII characters however.
      The  ASCII  code  table  can  be  extended  through  standardized
      techniques as described in FIPS Pub 35, Code Extension Techniques
      in 7 or 8 Bits [NatB-75].

                                     36

                                                        Section 4.1.3.1

      4.1.3.1  Printing-names

           Printing-Names  are  used  to  provide  labels  that  can be
      displayed  along  with  their  respective  data  elements.    For
      example, a message originator may use a Printing-Name property to
      request that the To field of a message be labeled "Distribution:"
      when it is printed by its recipients.

      4.1.3.2  Comments

           The  Comment  property  is  used  to  allow  comments  to be
      associated with any data element  without  affecting  its  actual
      contents.    For example, someone reviewing the text of a message
      could add the comment "This looks good" to the Text field without
      either altering the body itself  or  adding  a  separate  comment
      field.

      4.1.4  Data compression and encryption

           Two  constructor  data  elements,  Compressed and Encrypted,
      have  been  provided  for  use  by  a  CBMS  that  supports  data
      compression  or  encryption.    They  may  be  used  to  hold the
      compressed or encrypted contents of any data  element,  including
      Messages  and  Fields, and may occur wherever their compressed or
      encrypted contents may appear.  A mechanism is included to  allow
      the user to identify the encryption or compression algorithm used
      (Sections 4.3.4 and 4.3.5).

      4.2  Overview of Syntax Encoding

           This  section  provides  an  overview  of  the  notation and
      terminology  used  to  represent  the  syntactic  elements  (data
      elements) defined in this message format specification.

           All  data  elements consist of a series of components.  Each
      of the components is composed of a series of 8-bit groups  called
      octets.    In  this document, the bits are numbered starting from
      the low-order bit.  That is, the low-order (or least significant)
      bit is called "bit 0" and the high-order  (or  most  significant)
      bit is called "bit 7."  

           Five different components may appear in a data element.

        o  Identifier  octet  (identifying  particular type of data
           element)

                                     37

                                                            Section 4.2

        o  Length  Code  (specifying  number  of octets that appear
           following it in a data element)

        o  Qualifier (supplying additional identifying information)

        o  Property-List component (a  Property-List  data  element
           containing Property data elements)

        o  Data  Element  Contents  (containing  actual data of the
           data element)

      These components always appear in this order.  Not all components
      are present in all data elements, but  the  components  that  are
      present maintain this relative order.

      4.2.1  Identifier Octets

           The  identifier  octet  is  a numeric code containing infor-
      mation that identifies a data element.  It is  always  the  first
      component  in  a  data  element.  The Identifier octet contains a
      one-bit flag, indicating whether or not the data element contains
      a Property-List, and a  7-bit  unique  identifier  for  the  data
      element.  The value of the data element identifier also indicates
      whether the data element has a Qualifier.

           The  most significant bit (Bit 7) of the identifier octet is
      set to 1  if  there  are  properties  associated  with  the  data
      element;  it  is  set  to  0  if  there  are  none.   This bit is
      independent of the remaining seven bits in the identifier  octet,
      which  are  called  the  identifier, and provide unique identifi-
      cation  for  data  elements.    The  associated  properties   are
      specified in a Property-List component.

           The  second  most  significant bit (Bit 6) of the identifier
      octet  (the  most  significant  bit  of  the  identifier  itself)
      signifies  whether  or  not the data element has a Qualifier.  If
      the bit is set to 1, then the data element has a Qualifier; if it
      is a 0, the data element does not have a Qualifier.    The  seven
      bits of the identifier uniquely identify the data element.

           Table  2  shows  the  settings of the high-order bits of the
      identifier  octet  and  their  associated  meaning.    Figure   4
      demonstrates the bit-level structure of the identifier octet.  In
      this figure, bit 7 is indiciated with P to show its special use.

                                     38

                                                          Section 4.2.1

      -----------------------------------------------------------------

           bit 7 6 5 4 3 2 1 0
              +---------------+
              |P 0 x x x x x x|     0xxxxxx uniquely identifies a
              +---------------+     data element without a Qualifier.

              +---------------+
              |P 1 x x x x x x|     1xxxxxx uniquely identifies a
              +---------------+     data element with a Qualifier.

      FIG. 4.  STRUCTURE OF IDENTIFIER OCTETS

      -----------------------------------------------------------------

          Bit Value     Meaning

           7    0   The data element does not have properties asso-
                      ciated.
                1   The data element has properties associated.

           6    0   The data element does not have a Qualifier.
                1   The data element has a Qualifier.

          TABLE 2.  HIGH-ORDER BITS IN THE IDENTIFIER OCTET

      4.2.2  Length code and Qualifier components

           The Length Code and the Qualifier are both usually one octet
      in  length.    They use an encoding scheme that permits extending
      the component to the size necessary to represent  the  length  of
      the data element or the value of the Qualifier component.

           The  most  significant  bit  of the Length Code or Qualifier
      components determines whether it is  one  or  several  octets  in
      length.  When the most significant bit is 0, the component is one

                                     39

                                                          Section 4.2.2

      octet  in  length.  When the most significant bit is 1, the other
      seven bits of the first octet encode the number of octets in  the
      rest of the component.  The actual value begins in the next octet
      and is interpreted as an unsigned integer.

           A  single  octet  is  sufficient  for  most  Length Code and
      Qualifier components.  For those cases where  the  value  of  the
      Length  Code  or  the  Qualifier  must be greater than 127, extra
      octets can be added, up to a maximum of 127  octets.    Figure  5
      shows  the encoding scheme, as well as an example of a value less
      than 127 and one greater than 127.

      -----------------------------------------------------------------

           bit 7 6 5 4 3 2 1 0
              +---------------+
              |0 x x x x x x x|                   xxxxxxx is the value.
              +---------------+

              +---------------+------//-------+
              |1 n n n n n n n|y y y y y y y y|          nnnnnnn is the
              +---------------+------//-------+        number of octets
                                                       that contain the
                                                        value yyyyyyyy.

              +---------------+
              |0 0 0 0 1 0 0 1|               This is an example with a
              +---------------+                   value of 9 (decimal).

              +---------------+---------------+
              |1 0 0 0 0 0 0 1|1 0 0 0 0 0 1 0|      This example has a
              +---------------+---------------+ value of 130 (decimal).

              +---------------+---------------+
              |1 0 0 0 0 0 1 0|0 0 0 0 0 0 0 1|
              +---------------+---------------+

                              +---------------+
                              |0 0 1 0 1 1 0 0|      This example has a
                              +---------------+ value of 300 (decimal).

      FIG. 5.  ENCODING MECHANISM FOR QUALIFIERS AND LENGTH CODES

      -----------------------------------------------------------------

                                     40

                                                          Section 4.2.2

           In  order  to comply with this message format specification,
      CBMSs must be able to determine the value of any length  code  or
      qualifier  that  is  expressed  in  three  octets  or less.  (The

       16
      2  -1).    This message format specification places no limitation
      on the value of a length code or qualifier generated  by  a  CBMS
      (except  for  the  absolute  limitation inherent in the represen-
      tation scheme).  However, the use of length codes and  qualifiers
                                                                  32
      with  larger  values  (particularly  values  in  excess of 2  -1)
      should be avoided unless it is known that  the  receiving  system
      can handle them.  

           Both  Length  Codes and Qualifiers have a special convention
      for dealing with special situations.  Length  Codes  can  specify
      that  a  data  element  has indeterminate length; a Qualifier can
      specify that a data element is  implementation  defined.    These
      cases are explained further in the next two sections.

      4.2.2.1  Length Codes

           The length code component immediately follows the identifier
      octet.    It  is  present in every data element.  The Length Code
      indicates the number of octets following it  in  a  data  element
      (that  is,  excluding  the  identifier  octet and the length code
      itself).  Length Codes appear in one  of  three  formats:  short,
      long, and indefinite.

           A short Length Code is one octet long.  Its most significant
      bit  (Bit  7) is set to 0 and its value is in the range 0 through
      127.

           A long Length Code is at least two octets long.   The  first
      octet  always has its most significant bit (Bit 7) set to 1.  The
      other seven bits of this  octet  contain  the  number  of  octets
      making  up  the rest of the Length Code, and these octets contain

        1016
      (2     - 1) (that is, 127 octets to represent the value).

           An  indefinite  Length  Code  is  one  octet long.  Its most
      significant bit (Bit 7) is set to 1 and its other bits are all 0.
      (See Figure 6.)  An indefinite Length Code  may  appear  only  as
      part  of  a  constructor  data  element;  it  may  not occur in a

                                     41

                                                        Section 4.2.2.1

      -----------------------------------------------------------------

           bit 7 6 5 4 3 2 1 0
              +---------------+
              |0 x x x x x x x|             xxxxxxx is the value of the
              +---------------+                            length code.

              +---------------+------//-------+
              |1 n n n n n n n|y y y y y y y y|   nnnnnnn is the number
              +---------------+------//-------+  of octets that contain
                                                the value of the length
                                            code; these are represented
                                                            as yyyyyyy.
              +---------------+
              |1 0 0 0 0 0 0 0|            The "indefinite" length code
              +---------------+

      FIG. 6.  REPRESENTATION OF LENGTH CODES

      -----------------------------------------------------------------

                              5
      primitive  data  element .    A  constructor data element with an
      indefinite length code has an End-Of-Constructor data element  as
      the  last data element in its Data Element Contents.  (The length
      of such a constructor data element is unrestricted,  although  it
      must  contain at least one data element -- the End-of-Constructor
      that terminates it -- in its Data Element Contents.)

      4.2.2.2  Qualifier

           If present,the Qualifier component immediately  follows  the
      code  component.   It is used to provide information essential to
      the interpretation of the data element contents  that  is  beyond
      that  encoded  in  the  identifier  octet  or  length  code.  For
      example, the identifier octet could contain the code for a field,
      and the Qualifier component would specify what kind of field.

           The Qualifier component appears in only a few data elements.

      _______________

        5
         This is the result of most primitive elements  being  able  to
      contain  any  bit  pattern  (including the identifier for End-Of-
      Constructor).

                                     42

                                                        Section 4.2.2.2

      In the Bit-String data element, it indicates the number of unused
      bits  in  the  final  octet of the Data Element Contents.  In the
      Field and Property data elements, it  indicates  which  field  or
      property  the  data  element  represents.   In the Compressed and
      Encrypted  data  elements,  it  indicates  which  compression  or
      encryption algorithm has been used.  In the Message data element,
      it indicates the type of message.

           The  length  of  the  Qualifier  component  depends  on  the
      encoding of the Qualifier.  (See Figure 7.)  A short Qualifier is
      one octet long.  Its most significant bit is 0 and its  value  is
      in  the  range  0  through 127.  A long Qualifier is at least two
      octets in length.  The most significant bit is always 1  and  the
      other  7  bits  indicate the number of octets in the value of the
      Qualifier.

      -----------------------------------------------------------------

               +--------+--------+--------+
               |10000010|00000001 00001010|        Qualifier with value
               +--------+--------+--------+              266 (decimal).

               +--------+--------+--------+--------+
               |10000011|00000000|00000001 00001010|     Vendor-Defined
               +--------+--------+--------+--------+     Qualifier with
                                                             value 266.

               +--------+
               |10000000|              Undefined value for a Qualifier.
               +--------+

      FIG. 7.  EXAMPLES OF QUALIFIER VALUES

      -----------------------------------------------------------------

           This message format specification allows implementations  to
      define  their  own values for Qualifiers.  A vendor-defined Qual-
      ifier is any long Qualifier in which the first octet in the value
      is 0.    The  value  used  to  identify  this  Qualifier  is  not
      guaranteed  to  be  unique  and  the  same  value  may be used by
      different implementations to define different Qualifiers.

                                     43

                                                          Section 4.2.3

      4.2.3  Property-List

           A  Property  is  an attribute being associated with, but not
      essential  to  the  interpretation  of,  a  data  element.    The
      properties currently defined by this message format specification
      are  Printing-Name  and  Comment.  A Property-List component of a
      data element is represented by a Property-List data element  that
      in turn contains Property data elements.

           A data element contains at most one Property-List.  The most
      significant  bit  in  the  identifier  octet  of the data element
      indicates whether a Property-List is present.

      4.2.4  Data Element Contents

           The Data Element Contents component of a data element is the
      actual data or information represented by a data element.    (The
      other  components  provide  the information necessary to identify
      and interpret the Data Element Contents.)

           In a primitive data element, the Data Element Contents is  a
      series  of  octets  interpreted according to the identifier octet
      and any qualifier.

           In a constructor data element, the Data Element Contents  is
      a  series  of data elements.  When the Length Code component of a
      constructor data element is "indefinite," the last  data  element
      in the constructor's Data Element Contents is End-of-Constructor.

           The  length  of the Data Element Contents (in octets) is the
      difference between the value of the Length Code and  the  sum  of
      the following:

        o  the  length  of  the Qualifier component (depends on the
           data element)

        o  the length of the Property-List component.

      4.3  Data Element Syntax

           This message  format  specification  defines  nineteen  (19)
      different data elements.  Section 4.3.1 defines the encoding form
      for  data  elements  in  general  and  the  syntax  for each data
      element.  Section  4.3.2  describes  the  use  of  specific  data

                                     44

                                                            Section 4.3

      elements  as  part  of  the Data Element Contents of a Field data
      element.  A summary of the syntactic form appears in Appendix  F;
      summaries of the data element syntax appear in Appendix G.

      4.3.1  Data elements

           This  section  presents  the  general syntactic form for all
      data elements defined by this message  format  specification  and
      the detailed syntax for each data element.  The data elements are
      presented  by  syntactic  class: primitive data elements (Section
      4.3.1.1), constructors (Section 4.3.1.2), and data elements which
      can be either (Section 4.3.1.3).

           For convenience, the following terminology is used  in  this
      section.

                  Term            Meaning

              Primitive       a Primitive Data Element

              Constructor     a Constructor Data Element

              Element         any Data Element

           The  syntax  of  each  Element is presented in graphic form.
      The following conventions apply in the diagrams.  A single  octet
      is represented as follows.

          +--------+
          |        |
          +--------+

           Components that vary in length are represented as follows.

          +---//---+
          |        |
          +---//---+

           Each  Element  has  up to five components:  an Identifier, a
      Length Code, a Qualifier, a Property-List, and the  Data  Element
      Contents.

               In the diagrams, the contents of the identifier octet is

                                     45

                                                          Section 4.3.1

      shown  as  a "P" followed by an identifier represented in binary.
      (See Figure 4.)

      A length code is always represented in the following manner:

          +---//---+
          |Lxxxxxxx|
          +---//---+

      A qualifier is always represented in the following manner:

          +---//---+
          |Qxxxxxxx|
          +---//---+

      A Property-List (if  present)  always  immediately  precedes  any
      occurrence of Data Element Contents.

      The  Data  Element  Contents  appears  in  diagrams as one of the
      following:

        o  "element(s)", which may be any data element(s)

        o  "anything," which is undefined and  may  be  any  combi-
           nation of bits

        o  a specific data element

        o  the  interpretation to be applied to the bits within the
           octets that constitute the element  (such  as  ASCII  or
           Integer)

           Two  data  elements have been reserved for special purposes.
      The Extension data  element  is  provided  to  allow  for  future
      expansion of the possible data elements.  The Vendor-Defined data
      element  allows  CBMS  vendors to define their own data elements.
      Vendor-Defined data elements are not  guaranteed  to  be  unique,
      since  two  implementations  could define different data elements
      using the same identifier.  Vendor-Defined data  elements  should
      be used and interpreted by prior agreement.

           In  the  following  sections, each element is presented with
      its name, compliance  classification  (BASIC  or  OPTIONAL),  its
      identifier   (both   in   hexadecimal  and  in  octal),  a  brief
      description of its use, and a graphic representation.  Each  data
      element description has the following form.

                                     46

                                                          Section 4.3.1

      -----------------------------------------------------------------

      Data Element             (Compliance)   identifier   identifier
          Name                 ( Category )    octet         octet 
                                                    16            8

                     Description of the syntax of the data element.

                 +---//---+
                 |        |     Diagram representing data element
                 +---//---+

      -----------------------------------------------------------------

      4.3.1.1  Primitives

           The   data   elements   in  this  section  are  arranged  in
      alphabetical order by name.  (Appendix C presents the identifiers
      in numeric order.)

      ASCII-String             (BASIC)        02        002 
                                                16         8
                   This  data  element  contains  a  series  of   ASCII
                characters [NatB-80], each character right-justified in
                one  octet.    For  7-bit  ASCII  characters,  the most
                significant bit of each octet must be 0.

           Note: The ASCII code  table  can  be  extended  through
                standardized  techniques [NatB-75]  to  introduce addi-
                tional 7-bit or 8-bit  characters  or  additional  code
                tables.

                 +--------+---//---+----//-----+
                 |P0000010|Lxxxxxxx|ASCII chars|
                 +--------+---//---+----//-----+

                                     47

                                                        Section 4.3.1.1

      Bit-String               (OPTIONAL)     43        103 
                                                16         8
                This  data  element contains a series of bits.  It uses
                the Qualifier data  element  component  to  record  the
                number  of  bits  of  padding (as an eight bit unsigned
                integer) needed to fill the final  octet  of  the  Data
                Element  Contents  to  an  even  octet boundary.  These
                padding bits have no meaning and occur in the low order
                bits of the final octet.   The  valid  values  for  the
                Qualifier  component  are  0  through 7.  The number of
                bits in the Data Element Contents  is  calculated  from
                the following formula.

                8   *   number of octets   -   value of
                        in the Data            Qualifier component
                        Element Contents

                 +--------+---//---+---//---+---//---+
                 |P1000011|Lxxxxxxx|Qxxxxxxx|  bits  |
                 +--------+---//---+---//---+---//---+

      Boolean                  (OPTIONAL)     08        010 
                                                16         8
                This  data  element  contains  one octet whose value is
                either true or false.  False is represented by all bits
                being 0; true  is  represented  by  all  bits  being  1
                (although  any  non-zero value should be interpreted as
                true).

                 +--------+---//---+--------+
                 |P0001000|Lxxxxxxx| T or F |
                 +--------+---//---+--------+

      End-of-Constructor       (BASIC)        01        001 
                                                16         8
                This data element terminates the Data Element  Contents
                in  a  constructor  data  element  that  has indefinite
                length.  This data element has no  Contents  component.
                (Use of this element is described in Section 4.2.2.1.)

                 +--------+---//---+
                 |P0000001|Lxxxxxxx|
                 +--------+---//---+

                                     48

                                                        Section 4.3.1.1

      Integer                  (OPTIONAL)     20        040 
                                                16         8
                This  data element contains a 2's complement integer of
                variable  length,  high  order  octet  first.    It  is
                recommended  that the data element contents be either 2
                or 4 octets long whenever possible.

                 +--------+---//---+---//---+
                 |P0100000|Lxxxxxxx| Integer|
                 +--------+---//---+---//---+

      No-Op                    (OPTIONAL)     00        000 
                                                16         8
                This data element does nothing.  No-Op is used whenever
                it is necessary to include a data  element  that  means
                "no operation."  It is a short placeholder.

                 +--------+---//---+
                 |P0000000|Lxxxxxxx|
                 +--------+---//---+

      Padding                  (OPTIONAL)     21        041 
                                                16         8
                This data element is used to fill any number of octets.
                The  contents  of  a  Padding element are undefined and
                convey no information.

                 +--------+---//---+---//---+
                 |P0100001|Lxxxxxxx|anything|
                 +--------+---//---+---//---+

      4.3.1.2  Constructors

           The data elements in this section  are  arranged  in  alpha-
      betical order.

                                     49

                                                        Section 4.3.1.2

      Compressed               (OPTIONAL)     46        106 
                                                16         8
                This  data  element  must  contain  a  Bit-String  data
                element.  It is used to represent  any  data  that  has
                been   compressed;   it   may   be  used  wherever  its
                uncompressed contents may appear.    A  Qualifier  data
                component  appears  in each Compressed data element; it
                contains a  compression identifier  (CID)  to  identify
                the  compression  algorithm used.  (See Section 4.3.5.)
                The Data Element Contents contains the product  of  the
                compression process.

                 +--------+---//---+---//---+--------//--------+
                 |P1000110|Lxxxxxxx|Qxxxxxxx|Bit-String Element|
                 +--------+---//---+---//---+--------//--------+

      Date                     (BASIC)        28        050 
                                                16         8
                This   data   element  contains  an  ASCII-String  data
                element, which is a representation of a date  and  time
                formatted   in   accordance   with   PUBS  4 [NatB-68],
                58 [NatB-79a] and 59 [NatB-79b].  The use of  time  and
                time  zone is optional.  It is recommended that numeric
                offsets be used  to  indicate  time  zone  rather  than
                alphabetic abbreviations.

                 +--------+---//---+------//------+
                 |P0101000|Lxxxxxxx| ASCII-String |
                 +--------+---//---+------//------+

      Encrypted                (OPTIONAL)     47        107 
                                                16         8
                This  data  element  must  contain a Bit-String.  It is
                used to represent any data that has been encrypted;  it
                may  be  used  wherever  its  unencrypted  contents may
                appear.  A Qualifier data  component  appears  in  each
                Encrypted  data  element;  it  contains  an  encryption
                identifier (EID) identifying the  encryption  algorithm
                used.   The Data Element Contents is the product of the
                encryption process.

                 +--------+---//---+---//---+--------//--------+
                 |P1000111|Lxxxxxxx|Qxxxxxxx|Bit-String Element|
                 +--------+---//---+---//---+--------//--------+

                                     50

                                                        Section 4.3.1.2

      Field                    (BASIC)        4C        114 
                                                16         8
                This   data  element  uses  a  Qualifier  data  element
                component.  The Qualifier component  contains  a  Field
                Identifier  (FID)  indicating  which  specific field is
                being represented.

                 +--------+---//---+---//---+---//---+
                 |P1001100|Lxxxxxxx|Qxxxxxxx|elements|
                 +--------+---//---+---//---+---//---+

      Message                  (BASIC)        4D        115 
                                                16         8
                This data element may contain  Field  or  Message  data
                elements.    Its Qualifier component contains a Message
                type (MID) indicating the type of the  message.    (The
                MID is completely different from the message identifier
                in the Message-ID field and should not be confused with
                it.)

                 +--------+---//---+---//---+
                 |P1001101|Lxxxxxxx|Qxxxxxxx|
                 +--------+---//---+---//---+

                 +--------//---------//---------//---------//--------+
                 | Field, Message, Encrypted, or Compressed Elements |
                 +--------//---------//---------//---------//--------+

      Property-List            (OPTIONAL)     24        044 
                                                16         8
                This  data  element  contains a series of Property data
                elements to be associated with another data element.

                 +--------+---//---+-------//--------+
                 |P0100100|Lxxxxxxx|Property Elements|
                 +--------+---//---+-------//--------+

      Property                 (OPTIONAL)     45        105 
                                                16         8
                This  data  element  uses  a  Qualifier  data   element
                component.       The   Qualifier   component   contains
                a  Property-Identifier (PID) to indicate which specific
                property is being represented.

                 +--------+---//---+---//---+---//---+
                 |P1000101|Lxxxxxxx|Qxxxxxxx|elements|
                 +--------+---//---+---//---+---//---+

                                     51

                                                        Section 4.3.1.2

      Sequence                 (OPTIONAL)     0A        012 
                                                16         8
                This data element contains any series of data elements.
                Sequence  differs  from  Set  in that the data elements
                making up the Data Element Contents must be  considered
                as  an  ordered  sequence  (according to their order of
                appearance in the sequence.)

                 +--------+---//---+---//---+
                 |P0001010|Lxxxxxxx|elements|
                 +--------+---//---+---//---+

      Set                      (OPTIONAL)     0B        013 
                                                16         8
                This data element contains any series of data  elements
                with  no  ordering  of the elements implied.  (Sequence
                provides  an  ordered  series.)    Although  the   data
                elements   contained   in   a   Set   must   be  stored
                sequentially, the order in which they are stored is not
                defined and not processed.

                 +--------+---//---+---//---+
                 |P0001011|Lxxxxxxx|elements|
                 +--------+---//---+---//---+

      Unique-ID                (OPTIONAL)     09        011 
                                                16         8
                This data element is a unique identifier.  It need  not
                be human-readable.  The Data Element Contents may be an
                ASCII-String, a Bit-String, or an Integer.

                 +--------+---//---+---//---+
                 |P0001001|Lxxxxxxx| element|
                 +--------+---//---+---//---+

      4.3.1.3  Data Elements that Extend this Specification

           There  are  two  data  elements that are used to extend this
      specification.  They can be classified  as  either  primitive  or
      constructor data elements, depending on the extension.

                                     52

                                                        Section 4.3.1.3

      Extension                (OPTIONAL)     7E        176 
                                                16         8
                This  data  element  is  used  to  extend the number of
                available  data  elements  beyond  the  128  that   are
                possible   using  a  7-bit  identifier.    A  Qualifier
                component extends the encoding space  for  identifiers.
                (Extension and Vendor-Defined have the same syntax.)

                 +--------+---//---+---//---+---//---+
                 |P1111110|Lxxxxxxx|Qxxxxxxx|Anything|
                 +--------+---//---+---//---+---//---+

      Vendor-Defined           (OPTIONAL)     7F        177 
                                                16         8
                This  data  element  is  used  to represent vendor- and
                user-defined data  elements.    A  Qualifier  component
                extends  the  encoding  space  for  identifiers.    The
                Qualifier component is  not  guaranteed  to  be  unique
                among all interconnected systems.  This data element is
                interpreted   according   to  prior  agreement  between
                systems.  (Extension and Vendor-Defined  data  elements
                have the same syntax.)

                 +--------+---//---+---//---+---//---+
                 |P1111111|Lxxxxxxx|Qxxxxxxx|Anything|
                 +--------+---//---+---//---+---//---+

      4.3.2  Using data elements within message fields

           The Data Element Contents of a particular field in a message
      must  contain  at  least  one  data  element.   The types of data
      elements that can appear in the Data Element Contents of a  field
      are restricted according to what kind of field it is.  Appendix A
      (the  master  reference  appendix  for fields) defines which data
      elements are valid as the Contents for each of the fields.

           Some fields have  a  Data  Element  Contents  that  contains
      "originators"  or  "recipients."   No data element represents the
      identities of originators or recipients (because that encoding is
      not within the  scope  of  this  message  format  specification.)
      These  descriptions  simply  list  "originators" or "recipients",
      implying no restrictions on how the identifiers  for  originators
      or recipients are represented.

                                     53

                                                          Section 4.3.3

      4.3.3  Properties and associated elements

           This message format specification defines two properties.

      Comment                                 01        001 
                                                16         8
                This  property may contain any series of data elements;
                it most commonly contains one or more ASCII-Strings.

      Printing-Name                           02        002 
                                                16         8
                This property contains one ASCII-String.  In this case,
                the ASCII-String may contain only  the  printing  ASCII
                characters plus the "space" character.

      4.3.4  Encryption identifiers

           This  message  format  specification  defines two encryption
      identification codes.

      Unspecified                             00        000 
                                                16         8
                Use of  this  encryption  identifier  as  part  of  the
                Encrypted  data  element  indicates that the encryption
                method being used was not specified  for  inclusion  as
                part of the data element.

      FIPS-Standard                           01        001 
                                                16         8
                Use  of  this  encryption  identifier  as  part  of the
                Encrypted  data  element  indicates  that  the  Federal
                Information   Processing   Standard   method  for  data
                encryption was [NatB-77].

      4.3.5  Compression identifiers

           This message format specification  defines  one  compression
      identification code for use with the Compressed data element.

      Unspecified                             00        000 
                                                16         8
                Use  of  this  compression  identifier  as  part of the
                Compressed data element indicates that the  compression
                method  being  used  was not specified for inclusion as
                part of the data element.

                                     54

                                                          Section 4.3.6

      4.3.6  Message types

           This message format specification defines message type (MID)
      codes  for use in classifying the type of a message.  The message
      type could  be  confused  with  the  message  identifier  in  the
      Message-Id field; they are completely distinct concepts.

      FIPS-Standard                           01        01 
                                                16        8
                This  message  type  marks  messages  defined  by  this
                message format specification.

                                     55

                            SUMMARY OF APPENDIXES

      Appendix A  Defines  the  fields  in  the message format specifi-
                  cation.  This alphabetical appendix is for  reference
                  use   by   implementors.      It   contains  semantic
                  definitions of fields from  Section  3.1.    It  also
                  defines  Field  Identifier values and specifies which
                  data elements are valid as the Contents for  each  of
                  the fields.

      Appendix B  Defines  the  data  elements  in  the  message format
                  specification.  This alphabetically ordered  appendix
                  is  for  reference  use  by implementors.  It consol-
                  idates information from Section 4.3.

      Appendix C  Provides a reference table listing the data  elements
                  in numerical order by their identifier octets.

      Appendix D  Provides a reference table summarizing the components
                  of messages according to whether they are required or
                  optional for CBMSs implementing the specification.

      Appendix E  Provides  a  reference  table  organizing the message
                  components according to the functional class  of  the
                  components.

      Appendix F  Provides   an  overview  of  the  syntactic  elements
                  defined by this message format specification.

      Appendix G  Summarizes syntactic elements  according  to  whether
                  they are required or optional for a CBMS implementing
                  the message format specification.

      Appendix H  Examples  of  each syntactic element displaying their
                  syntax and describing their associated semantics.

                                     56

                                                             Appendix A

                                 APPENDIX A
                  FIELDS -- IMPLEMENTORS' MASTER REFERENCE

           This  appendix  defines  all  of  the  fields in the message
      format specification for  reference  use  by  implementors.    It
      contains  semantics  definitions  of fields from Section 3.1.  It
      also defines Field Identifier values and which data elements  are
      valid  as  the  Contents  for  each  of  the  fields.   The field
      definitions appear alphabetically.

           Each field in the list has the following form:

      ------------------------------------------------------------

      Field Name               Compliance   identifier  identifier
                                              value       value 
                                                   16          8

                   Description of the field semantics.   Names  of
              data  elements  that  are  valid in the Data Element
              Contents of this kind of field.

      ------------------------------------------------------------

      Attachments              OPTIONAL       08        010 
                                                16         8
                This field  contains  additional  data  accompanying  a
                message.    It  is similar in intent to enclosures in a
                conventional mail system.  Contents of this  field  are
                unrestricted.

      Author                   OPTIONAL       0C        014 
                                                16         8
                This  field  identifies the individual(s) who wrote the
                primary contents of the message.   Use  of  the  Author
                field  is  discouraged  when the contents of the Author
                field and the From field would be completely redundant.
                This field contains one or more originator identities.

                                     57

                                                             Appendix A

      Bcc                      OPTIONAL       0D        015 
                                                16         8
                This  field  identifies  additional  recipients  for  a
                message (a "blind carbon copies list").   The  contents
                of  this  field are not to be included in copies of the
                message sent to the primary and  secondary  recipients.
                See  section 3.2.1 for further discussion of the use of
                blind carbon copies lists. This field contains  one  or
                more recipient identities.

      Cc                       BASIC          06        006 
                                                16         8
                This   field  identifies  secondary  recipients  for  a
                message (a "carbon copies" list).  This field  contains
                one or more recipient identities.

      Circulate-Next           OPTIONAL       0E        016 
                                                16         8
                This field is used in conjunction with the Circulate-To
                field.    (See Section 3.2.6.1 for further discussion.)
                It identifies all recipients in a circulation list  who
                have not yet received the message.  This field contains
                one or more recipient identities.

      Circulate-To             OPTIONAL       0F        017 
                                                16         8
                This  field  identifies  recipients  for  a  circulated
                message.  (See Section 3.2.6.1 for further discussion.)
                It is  used  in  conjunction  with  the  Circulate-Next
                field.    This  field  contains  one  or more recipient
                identities.

      Comments                 OPTIONAL       10        020 
                                                16         8
                This field permits adding  comments  onto  the  message
                without   disturbing   the  original  contents  of  the
                message.  While the Comments field will usually contain
                one or more ASCII-Strings, there are no restrictions on
                its contents.

      Date                     OPTIONAL       11        021 
                                                16         8
                This  field  contains  a  date   that   the   message's
                originator  wishes  to  associate  with a message.  The
                Date field is to the Posted-Date field as the date on a
                letter is to the postmark added  by  the  post  office.
                This field contains one Date.

                                     58

                                                             Appendix A

      End-Date                 OPTIONAL       12        022 
                                                16         8
                This  field  contains the date on which a message loses
                effect.    (See  also   Section   3.2.5   for   further
                discussion.)  This field contains one Date.

      From                     REQUIRED       01        001 
                                                16         8
                This  field  contains  the  identity of the originators
                taking formal responsibility for  this  message.    The
                contents  of  the  From field is to be used for replies
                when no Reply-to field appears  in  a  message.    This
                field contains one or more originator identities.

      In-Reply-To              OPTIONAL       13        023 
                                                16         8
                This  field designates previous correspondence to which
                this message is a reply.  The usual  contents  of  this
                field  would be the contents of the Message-ID field of
                the message(s) being replied to.  This  field  contains
                one or more Unique-IDs or ASCII-Strings.

      Keywords                 OPTIONAL       14        024 
                                                16         8
                This  field  contains  keywords  or  phrases for use in
                retrieving a message.  This field contains one or  more
                ASCII-Strings.   (Each keyword or phrase is represented
                by a separate ASCII-String.)

      Message-Class            OPTIONAL       15        025 
                                                16         8
                This field indicates the purpose of  a  message.    For
                example,  it  might  contain values indicating that the
                message is a memorandum or a  data-base  entry.    This
                field contains one data element, an ASCII-String.

      Message-ID               OPTIONAL       16        026 
                                                16         8
                This  field contains a unique identifier for a message.
                This identifier is intended for machine generation  and
                processing.    Further  definition  appears  in Section
                3.2.4.1.  Only one Message-ID field is permitted  in  a
                message.    This  field  contains  one  data element, a
                Unique-ID.

      Obsoletes                OPTIONAL       26        046 
                                                16         8
                This field identifies one or more  messages  that  this
                one  supplants.    This  field  contains  at  least one
                Unique-ID and may contain more than one.

                                     59

                                                             Appendix A

      Originator-Serial-Number OPTIONAL       17        027 
                                                16         8
                This field contains one or more serial numbers assigned
                by  the  message's originator.  (Messages with multiple
                recipients should  all  have  the  same  value  in  the
                Originator-Serial-Number  field.    This field contains
                one or more ASCII-Strings.  (One ASCII-String  is  used
                for each serial number.)

      Posted-Date              REQUIRED       02        002 
                                                16         8
                This  field  contains  the  posting  date, which is the
                point in time  when  the  message  passes  through  the
                posting  slot into a message transfer system.  Only one
                Posted-Date field is permitted  in  a  message.    This
                field contains one Date.

      Precedence               OPTIONAL       18        030 
                                                16         8
                Ordinarily, message precedence or priority is a service
                request  to  a  message  transfer  system.    A message
                originator, however, can include precedence information
                in a message.  This field indicates the  precedence  at
                which  the  message  was  posted.    One  example  of a
                precedence  scheme  is  the  US   Military   categories
                "ROUTINE",  "PRIORITY",  "IMMEDIATE", "FLASH OVERRIDE",
                and  "EMERGENCY  COMMAND  PRECEDENCE".     This   field
                contains one ASCII-String.

      Received-Date            OPTIONAL       19        031 
                                                16         8
                This  field  is  also  called Delivery date.  It may be
                added to a message by the recipient's message receiving
                program.   It  indicates  when  the  message  left  the
                delivery  system  and  entered  the recipient's message
                processing domain.  This field contains one Date.

      Received-From            OPTIONAL       1A        032 
                                                16         8
                This field  contains  a  record  of  a  message's  path
                through    a    message    transfer    system.      The
                recipient's message receiving  program  may  store  any
                such   information  that  it  obtains  from  a  message
                transfer system in this field.  The  contents  of  this
                field are unrestricted.

                                     60

                                                             Appendix A

      References               OPTIONAL       20        040 
                                                16         8
                This  field  identifies  other correspondence that this
                message  references.    If  the  other   correspondence
                contains  a  Message-ID  field,  the  contents  of  the
                References field must be the message identifier.   This
                field contains one or more Unique-IDs or ASCII-Strings.

      Reissue-Type             OPTIONAL       25        045 
                                                16         8
                This   field   is  used  in  conjunction  with  message
                encapsulating  (see  Section  3.2.2)  to  differentiate
                between messages being assigned or redistributed.  This
                field  contains  one  data  element,  usually an ASCII-
                String.

      Reply-To                 BASIC          03        003 
                                                16         8
                This field identifies any recipients for replies to the
                message.  This field contains  one  or  more  recipient
                identities.

      Sender                   OPTIONAL       22        042 
                                                16         8
                This  field  identifies the agent who sent the message.
                It is intended either for when the sender  is  not  the
                originator  responsible  for the message or to indicate
                who among a group of originators  responsible  for  the
                message  actually  sent it.  Use of the Sender field is
                discouraged when the contents of the Sender  field  and
                From  field  would  be  completely redundant.  Only one
                Sender field is permitted in a  message.    This  field
                contains one originator identity.

      Start-Date               OPTIONAL       23        043 
                                                16         8
                This  field  contains the date on which a message takes
                effect.  (See Section 3.2.5  for  further  discussion.)
                This field contains one Date.

      Subject                  BASIC          07        007 
                                                16         8
                This field contains whatever information the originator
                provided  to  summarize  or  indicate the nature of the
                message.   This  field  contains  one  or  more  ASCII-
                Strings.

      Text                     BASIC          04        004 
                                                16         8
                This field contains the primary content of the message.
                Contents of this field are unrestricted.

                                     61

                                                             Appendix A

      To                       REQUIRED       05        005 
                                                16         8
                This field identifies primary recipients for a message.
                This field contains one or more recipient identities.

      Warning-Date             OPTIONAL       24        044 
                                                16         8
                This  field is used either alone or in conjunction with
                an End-Date field.  It  contains  one  or  more  dates.
                These  dates  could  be  used  by  a message processing
                program as warnings of an impending end-date  or  other
                event.    (See  Section  3.2.5 for further discussion.)
                This field contains one or more Dates.

                                     62

                                                             Appendix B

                                 APPENDIX B
               DATA ELEMENTS -- IMPLEMENTORS' MASTER REFERENCE

           The appendix defines all of the data elements in the message
      format  specification,  for  reference  use  by implementors.  It
      contains no new information but rather consolidates the syntactic
      information from Section 4.3.

           Each data element description has the following form.

      -----------------------------------------------------------------

      Data Element        (Compliance)   identifier   identifier
          Name            ( Category )    octet         octet 
                                               16            8

                Constructive class (primitive or constructor)

                Description of the syntax of the data element.

                +---//---+
                |        |     Diagram representing data element
                +---//---+

      -----------------------------------------------------------------

                                     63

                                                             Appendix B

      ASCII-String             (BASIC)        02        002 
                                                16         8
                primitive

                This data element contains a series of ASCII characters
                 [NatB-80],   each  character  right-justified  in  one
                octet.    For  7-bit   ASCII   characters,   the   most
                significant bit of each octet must be 0.

                Note:  The  ASCII  code  table  can be extended through
                standardized techniques [NatB-75]  to  introduce  addi-
                tional  7-bit  or  8-bit  characters or additional code
                tables.

                 +--------+---//---+----//-----+
                 |P0000010|Lxxxxxxx|ASCII chars|
                 +--------+---//---+----//-----+

      Bit-String               (OPTIONAL)     43        103 
                                                16         8
                primitive

                This data element contains a series of bits.   It  uses
                the  Qualifier  data  element  component  to record the
                number  of  bits  of  padding  (as  an  8-bit  unsigned
                integer)  needed  to  fill  the final octet of the Data
                Element Contents to an  even  octet  boundary.    These
                padding bits have no meaning and occur in the low order
                bits  of  the  final  octet.   The valid values for the
                Qualifier component are 0 through 7.    The  number  of
                bits  in  the  Data Element Contents is calculated from
                the following formula.

                8   *   number of octets   -   value of
                        in the Data            Qualifier component
                        Element Contents

                 +--------+---//---+---//---+---//---+
                 |P1000011|Lxxxxxxx|Qxxxxxxx|  bits  |
                 +--------+---//---+---//---+---//---+

                                     64

                                                             Appendix B

      Boolean                  (OPTIONAL)     08        010 
                                                16         8
                primitive

                This  data  element  contains  one octet whose value is
                either true or false.  False is represented by all bits
                being 0; true  is  represented  by  all  bits  being  1
                (although  any  non-zero value should be interpreted as
                true).

                 +--------+---//---+--------+
                 |P0001000|Lxxxxxxx| T or F |
                 +--------+---//---+--------+

      Compressed               (OPTIONAL)     46        106 
                                                16         8
                constructor

                This  data  element  must  contain  a  Bit-String  data
                element.    It  is  used to represent any data that has
                been  compressed;  it  may   be   used   wherever   its
                uncompressed  contents  may  appear.   A Qualifier data
                component appears in each Compressed data  element;  it
                contains a compression identifier (CID) to identify the
                compression  algorithm used.  (See Section 4.3.5.)  The
                Data Element  Contents  contains  the  product  of  the
                compression process.

                 +--------+---//---+---//---+--------//--------+
                 |P1000110|Lxxxxxxx|Qxxxxxxx|Bit-String Element|
                 +--------+---//---+---//---+--------//--------+

      Date                     (BASIC)        28        050 
                                                16       8
                constructor

                This   data   element  contains  an  ASCII-String  data
                element, which is a representation of a date  and  time
                formatted  in  accordance  with  FIPS PUBS 4 [NatB-68],
                58 [NatB-79a], and 59 [NatB-79b].  The use of time  and
                time  zone is optional.  It is recommended that numeric
                offsets be used  to  indicate  time  zone  rather  than
                alphabetic abbreviations.

                 +--------+---//---+------//------+
                 |P0101000|Lxxxxxxx| ASCII-String |
                 +--------+---//---+------//------+

                                     65

                                                             Appendix B

      Encrypted                (OPTIONAL)     47        107 
                                                16         8
                constructor

                This  data  element  must  contain a Bit-String.  It is
                used to represent any data that has been encrypted;  it
                may  be  used  wherever  its  unencrypted  contents may
                appear.  A Qualifier data  component  appears  in  each
                Encrypted  data  element;  it  contains  an  encryption
                identifier (EID) identifying the  encryption  algorithm
                used.  (See Section 4.3.4 for further discussion.)  The
                Data  Element Contents is the product of the encryption
                process.

                 +--------+---//---+---//---+--------//--------+
                 |P1000111|Lxxxxxxx|Qxxxxxxx|Bit-String Element|
                 +--------+---//---+---//---+--------//--------+

      End-of-Constructor       (BASIC)        01        001 
                                                16         8
                primitive

                This data element terminates the Data Element  Contents
                in  a  constructor  data  element  that  has indefinite
                length.  This data element has no  Contents  component.
                (Use of this element is described in Section 4.2.2.1.)

                 +--------+---//---+
                 |P0000001|Lxxxxxxx|
                 +--------+---//---+

      Extension                (OPTIONAL)     7E        176 
                                                16         8
                either

                This  data  element  is  used  to  extend the number of
                available  data  elements  beyond  the  128  that   are
                possible   using  a  7-bit  identifier.    A  Qualifier
                component extends the encoding space  for  identifiers.
                (Extension and Vendor-Defined have the same syntax.)

                 +--------+---//---+---//---+---//---+
                 |P1111110|Lxxxxxxx|Qxxxxxxx|Anything|
                 +--------+---//---+---//---+---//---+

                                     66

                                                             Appendix B

      Field                    (BASIC)        4C        114 
                                                16         8
                constructor

                This   data  element  uses  a  Qualifier  data  element
                component.  The Qualifier component  contains  a  Field
                Identifier  (FID)  indicating  which  specific field is
                being represented.   (See  Section  4.3.2  for  further
                discussion.)

                 +--------+---//---+---//---+---//---+
                 |P1001100|Lxxxxxxx|Qxxxxxxx|elements|
                 +--------+---//---+---//---+---//---+

      Integer                  (OPTIONAL)     20        040 
                                                16         8
                primitive

                This  data element contains a 2's complement integer of
                variable  length,  high-order  octet  first.    It   is
                recommended  that the data element contents be either 2
                or 4 octets long whenever possible.

                 +--------+---//---+---//---+
                 |P0100000|Lxxxxxxx| Integer|
                 +--------+---//---+---//---+

      Message                  (BASIC)        4D        115 
                                                16         8
                constructor

                This data element may contain  Field  or  Message  data
                elements.    Its Qualifier component contains a Message
                type (MID) indicating the type of the  message.    (See
                Section  4.3.6  for  further  discussion.)  (The MID is
                completely different from the message identifier in the
                Message-ID field and should not be confused with it.)

                 +--------+---//---+---//---+
                 |P1001101|Lxxxxxxx|Qxxxxxxx|
                 +--------+---//---+---//---+

                 +--------//---------//---------//---------//--------+
                 | Field, Message, Encrypted, or Compressed Elements |
                 +--------//---------//---------//---------//--------+

                                     67

                                                             Appendix B

      No-Op                    (OPTIONAL)     00        000 
                                                16         8
                primitive

                This data element does nothing.  No-Op is used whenever
                it  is  necessary  to include a data element that means
                "no operation."  It is a short placeholder.

                 +--------+---//---+
                 |P0000000|Lxxxxxxx|
                 +--------+---//---+

      Padding                  (OPTIONAL)     21        041 
                                                16         8
                primitive

                This data element is used to fill any number of octets.
                The contents of a Padding  element  are  undefined  and
                convey no information.

                 +--------+---//---+---//---+
                 |P0100001|Lxxxxxxx|anything|
                 +--------+---//---+---//---+

      Property-List            (OPTIONAL)     24        044 
                                                16         8
                constructor

                This  data  element  contains a series of Property data
                elements to be associated with another data element.

                 +--------+---//---+-------//--------+
                 |P0100100|Lxxxxxxx|Property Elements|
                 +--------+---//---+-------//--------+

                                     68

                                                             Appendix B

      Property                 (OPTIONAL)     45        105 
                                                16         8
                constructor

                This   data  element  uses  a  Qualifier  data  element
                component.      The   Qualifier   component    contains
                a  Property-Identifier (PID) to indicate which specific
                property  is being represented.  (See Section 4.3.3 for
                further discussion.)

                 +--------+---//---+---//---+---//---+
                 |P1000101|Lxxxxxxx|Qxxxxxxx|elements|
                 +--------+---//---+---//---+---//---+

      Sequence                 (OPTIONAL)     0A        012 
                                                16         8
                constructor

                This data element contains any series of data elements.
                Sequence differs from Set in  that  the  data  elements
                making  up the Data Element Contents must be considered
                as an ordered sequence (according  to  their  order  of
                appearance in the sequence.)

                 +--------+---//---+---//---+
                 |P0001010|Lxxxxxxx|elements|
                 +--------+---//---+---//---+

      Set                      (OPTIONAL)     0B        013 
                                                16         8
                constructor

                This  data element contains any series of data elements
                with no ordering of the elements  implied.    (Sequence
                provides   an  ordered  series.)    Although  the  data
                elements  contained   in   a   Set   must   be   stored
                sequentially, the order in which they are stored is not
                defined and not processed.

                 +--------+---//---+---//---+
                 |P0001011|Lxxxxxxx|elements|
                 +--------+---//---+---//---+

                                     69

                                                             Appendix B

      Unique-ID                (OPTIONAL)     09        011 
                                                16         8
                constructor

                This  data element is a unique identifier.  It need not
                be human-readable.  The Data Element Contents may be an
                ASCII-String, a Bit-String, or an Integer.

                 +--------+---//---+---//---+
                 |P0001001|Lxxxxxxx| element|
                 +--------+---//---+---//---+

      Vendor-Defined           (OPTIONAL)     7F        177 
                                                16         8
                either

                This data element is used to  represent  vendor-defined
                data  elements.    A  Qualifier  component  extends the
                encoding  space  for  identifiers.      The   Qualifier
                component  is  not  guaranteed  to  be unique among all
                interconnected  systems.     This   data   element   is
                interpreted   according   to  prior  agreement  between
                systems.  (Extension and Vendor-Defined  data  elements
                have the same syntax.)

                 +--------+---//---+---//---+---//---+
                 |P1111111|Lxxxxxxx|Qxxxxxxx|Anything|
                 +--------+---//---+---//---+---//---+

                                     70

                                                             Appendix C

                                 APPENDIX C
                       DATA ELEMENT IDENTIFIER OCTETS

      Identifier  Identifier  Data Element Name

      00          000         No-Op
      01          001         End-of-Constructor
      02          002         ASCII-String
      08          010         Boolean
      09          011         Unique-ID
      0A          012         Sequence
      0B          013         Set
      20          040         Integer
      21          041         Padding
      24          044         Property-List
      28          050         Date
      43          103         Bit-String
      45          105         Property
      46          106         Compressed
      47          107         Encrypted
      4C          114         Field
      4D          115         Message
      7E          176         Extension
      7F          177         Vendor-Defined

                                     71

                                                             Appendix D

                                 APPENDIX D
              SUMMARY OF MESSAGE FIELDS BY COMPLIANCE CATEGORY

           This  appendix  is  for  reference  use.  It contains no new
      information, but rather abstracts from that presented in  Section
      3.1.

           This  appendix  contains  the  message  field names arranged
      alphabetically within compliance category.   (Appendix  E  orders
      the  field  names  within  functional  category.)  Complete field
      definitions appear in Appendix A.

           Required fields must appear in a message.  Basic fields must
      be recognized and processed by all CBMS systems.  Optional fields
      need not be supported by  a  CBMS  but,  if  supported,  must  be
      processed according to the meanings defined by the message format
      specification.

      D.1  REQUIRED Fields

      From
      Posted-Date
      To

      D.2  BASIC Fields

      Cc
      Reply-To
      Subject
      Text

      D.3  OPTIONAL Fields

      Attachments
      Author
      Bcc
      Circulate-Next
      Circulate-To
      Comments

                                     72

                                                             Appendix D

      Date
      End-Date
      In-Reply-To
      Keywords
      Message-Class
      Message-ID
      Obsoletes
      Originator-Serial-Number
      Precedence
      Received-Date
      Received-From
      References
      Reissue-Type
      Sender
      Start-Date
      Warning-Date

                                     73

                                                             Appendix E

                                 APPENDIX E
                  SUMMARY OF MESSAGE SEMANTICS BY FUNCTION

           This  appendix  is  for  reference  use.  It contains no new
      information, but rather abstracts from that presented in  Section
      3.1.

           This  appendix  contains  the  message  field names arranged
      alphabetically within functional class.  (Appendix D  orders  the
      field names within compliance class.)  Complete field definitions
      appear in Appendix A.

      E.1  Circulation

      Circulate-Next
      Circulate-To

      E.2  Cross-Referencing

      In-Reply-To
      Message-ID
      Obsoletes
      Originator-Serial-Number
      References

      E.3  Life Spans

      End-Date
      Start-Date
      Warning-Date

      E.4  Delivery System

      Received-Date
      Received-From

                                     74

                                                             Appendix E

      E.5  Miscellaneous Fields Used Generally

      Attachments
      Comments
      Keywords
      Message-Class
      Precedence
      Subject
      Text

      E.6  Reply Generation

      Reply-To

      E.7  Reissuing

      Reissue-Type

      E.8  Sending (Normal Transmission)

      Author
      Bcc
      Cc
      Date
      From
      Posted-Date
      Sender
      To

                                     75

                                                             Appendix F

                                 APPENDIX F
                       SUMMARY OF DATA ELEMENT SYNTAX

           This  appendix summarizes data element syntax by diagramming
      the components of data elements.  Detailed presentation  of  data
      element syntax appears in Section 4.3.1.

           In  these  diagrams,  required  components of a data element
      appear as follows.  (The double border signifies "required.")

                +========+        +===//===+
                |        |        |        |
                +========+        +===//===+
                always one        one or more
                octet long        octets long

           Optional components of  data  elements  are  represented  as
      follows.  (The single border signifies "not required.")

                +--------+        +---//---+
                |        |        |        |
                +--------+        +---//---+
                always one        one or more
                octet long        octets long

           The  first  octet in a data element is the identifier octet.
      In diagrams of data elements, all eight bits  of  the  identifier
      octet  are  always  shown.  Bits with fixed values show the fixed
      values as 1s and 0s.  Bits with variable values are shown as  x's
      and y's.

           The  first  bit  in  an  identifier octet is the P-bit.  Its
      value indicates whether a data element contains a property  list.
      (A  P-bit  value of 1 indicates the presence of a property list.)
      The remaining seven bits contain the rest of the identifier.

           Other octets in  a  data  element  belong  to  one  of  four
      classes:    Length  Code, Qualifier, Property-List, and Contents.
      In diagrams of syntax the data  element  components  are  labeled
      according to their class.

                                     76

                                                             Appendix F

           Component Class             Label

          Length code                  Length
          Qualifier                    Qual
          Property-List                P-List
          Contents                     Contents

           Data elements must follow this form.

                +========+===//===+---//---+---//---+---//---+
                |Pxxxxxxx| Length |  Qual  | P-List |contents|
                +========+===//===+---//---+---//---+---//---+

      The  value  of the Length component is the total number of octets
      following the length code octet in the data element.

                                     77

                                                             Appendix G

                                 APPENDIX G
               SUMMARY OF DATA ELEMENTS BY COMPLIANCE CATEGORY

           Compliance  categories  for syntactic elements are basic and
      optional.  Every CBMS is required to recognize and process  basic
      elements.    A  CBMS is not required to process optional elements
      although many are strongly recommended by the semantics.

           This appendix  summarizes  data  elements  by  listing  them
      according to their compliance category.

      G.1  BASIC Data Elements

      ASCII-String             (primitive)    02        002 
                                                16         8
      Date                     (constructor)  28        050 
                                                16         8
      End-Of-Constructor       (primitive)    01        001 
                                                16         8
      Field                    (constructor)  4C        114 
                                                16         8
      Message                  (constructor)  4D        115 
                                                16         8

      G.2  OPTIONAL Data Elements

      Bit-String               (primitive)    43        103 
                                                16         8
      Boolean                  (primitive)    08        010 
                                                16         8
      Compressed               (constructor)  46        106 
                                                16         8
      Encrypted                (constructor)  47        107 
                                                16         8
      Extension                (either)       7E        176 
                                                16         8
      Integer                  (primitive)    20        040 
                                                16         8
      No-Op                    (primitive)    00        000 
                                                16         8
      Padding                  (primitive)    21        041 
                                                16         8

                                     78

                                                             Appendix G

      Property                 (constructor)  45        105 
                                                16         8
      Property-List            (constructor)  24        044 
                                                16         8
      Sequence                 (constructor)  0A        012 
                                                16         8
      Set                      (constructor)  0B        013 
                                                16         8
      Unique-ID                (constructor)  09        011 
                                                16         8
      Vendor-Defined           (either)       7F        377 
                                                16         8

                                     79

                                                             Appendix H

                                 APPENDIX H
                                  EXAMPLES

           This  appendix presents at least one example for each of the
      data elements defined in this message format specification.    In
      these examples, identifier octets are represented in binary form.
      All  other  numbers  are presented in hexadecimal.  ASCII strings
      are shown as characters rather  than  their  numerical  represen-
      tation.    Although  this  message  format specification does not
      define the syntax of names and addresses, message originators and
      recipients are identified by their names.  This  does  not  imply
      anything  about  how naming and addressing can or should be done;
      it is simply a convenient way to identify message originators and
      recipients in these examples.

      H.1  Primitive Data Elements

           This section contains an example of each  of  the  primitive
      data  elements.   Each example contains a short explanation and a
      series of octets.

           No-Op data element:

           +--------+--------+
           |00000000|00000000|
           +--------+--------+

           End-of-Constructor data element:

           +--------+--------+
           |00000001|00000000|
           +--------+--------+

                                     80

                                                             Appendix H

           Boolean data element whose value is true:

           +--------+--------+--------+
           |00001000|00000001|11111111|
           +--------+--------+--------+

           Integer  data  element  containing five octets of data.  Its
      value is 4,294,967,296 (decimal):

           +--------+--------+--------+--------+--------+
           |00100000|  0   5 |  0   1    0   0    0   0
           +--------+--------+--------+--------+--------+

                    +--------+--------+
                       0   0    0   0 |
                    +--------+--------+

           Padding data element containing  three  octets  of  padding.
      The values of those three octets are meaningless:

           +--------+--------+--------+--------+--------+
           |00100001|  0   3 |  F   F    F   F    F   F |
           +--------+--------+--------+--------+--------+

           ASCII-String  data  element containing nine characters.  Its
      value is "Hi There.":

           +--------+--------+---- ----+
           |00000010|  0   9 |Hi There.|
           +--------+--------+---- ----+

                                     81

                                                             Appendix H

           Bit-String data element containing 44 bits of data (((7-1) x
      8)  - 4).  Six octets are used to hold those 44 bits.  The last 4
      bits in the final octet are padding and are therefore ignored.

           Bit-String  Length   Spare
           +--------+--------+--------+--------+--------+
           |01000011|  0   7 |  0   4 |  0   A    3   B
           +--------+--------+--------+--------+--------+

                    +--------+--------+--------+--------+
                       5   F    2   9    1   C    D   0 |
                    +--------+--------+--------+--------+

      H.2  Constructor Data Elements

           This section contains an example of each of the  constructor
      data  elements.    Each  example contains a short explanation and
      then an annotated series of  the  data  elements  making  up  the
      constructor.

           Property-List  data  element  containing  one  Property data
      element.    The  property  is  Printing-Name  and  its  value  is
      "Distribution":

           Prop-List  Length  Property  Length    PID
           +--------+--------+--------+--------+--------+
           |00100100|  1   1 |01000101|  0   F |  0   2 |
           +--------+--------+--------+--------+--------+

                      ASCII    Length
                    +--------+--------+----    ----+
                    |00000010|  0   C |Distribution|
                    +--------+--------+----    ----+

                                     82

                                                             Appendix H

           Printing-Name  Property.   The value of the Printing-Name is
      "Distribution":

            Property  Length    PID     ASCII    Length
           +--------+--------+--------+--------+--------+
           |01000101|  0   F |  0   2 |00000010|  0   C |
           +--------+--------+--------+--------+--------+

                    +----    ----+
                    |Distribution|
                    +----    ----+

           Compressed data element.  Its contents were compressed using
      an unspecified data compression algorithm.  The  compressed  data
      is in a bit-string that is 56 bits long, fully filling 7 octets:

           Compressed  Length   CID   Bit-String  Length
           +--------+--------+--------+--------+--------+
           |01000110|  0   B |  0   0 |01000011|  0   8 |
           +--------+--------+--------+--------+--------+

                       Spare
                    +--------+--------+--------+--------+
                    |  0   0 |  1   C    5   F    2   D
                    +--------+--------+--------+--------+

                    +--------+--------+--------+--------+
                       7   7    B   A    F   6    2   9 |
                    +--------+--------+--------+--------+

                                     83

                                                             Appendix H

           Encrypted  data  element.    The  encryption  method used to
      encrypt its contents has been intentionally not specified.   This
      element contains a Bit-String which contains 22 bits (((4-1) x 8)
      - 2) of data.  These 22 bits are represented in octets; the final
      2 bits in the final octet are padding and are therefore ignored:

           Encrypted   Length   EID   Bit-String  Length
           +--------+--------+--------+--------+--------+
           |01000111|  0   7 |  0   0 |01000011|  0   4 |
           +--------+--------+--------+--------+--------+

                       Spare
                    +--------+--------+--------+--------+
                    |  0   2 |  A   3    7   8    1   C |
                    +--------+--------+--------+--------+

           Date  data  element.    This  example includes a date but no
      time.  The date shown in this example is August 15, 1980:

             Date     Length   ASCII    Length
           +--------+--------+--------+--------+---  ---+
           |00101000|  0   A |00000010|  0   8 |19800815|
           +--------+--------+--------+--------+---  ---+

           Unique-ID data element, which is represented as  an  Integer
      data element whose value is 129 (decimal).

           Unique-ID  Length   Integer  Length
           +--------+--------+--------+--------+--------+--------+
           |00001001|  0   4 |00100000|  0   2 |  0   0    8   1 |
           +--------+--------+--------+--------+--------+--------+

                                     84

                                                             Appendix H

           Sequence  data element containing two ASCII-String data ele-
      ments.  The first ASCII-String is  "This  is"  while  the  second
      string is " a list":

            Sequence  Length   ASCII    Length
           +--------+--------+--------+--------+--- ---+
           |00001010|  1   2 |00000010|  0   7 |This is|
           +--------+--------+--------+--------+--- ---+

                      ASCII    Length
                    +--------+--------+--- ---+
                    |00000010|  0   7 | a list|
                    +--------+--------+--- ---+

           Set  data element containing two Integer data elements.  The
      first integer has a value of 519 (decimal) while the value of the
      second is 71 (decimal).   (These  two  values  have  no  ordering
      because they belong to a set.)

              Set     Length   Integer  Length
           +--------+--------+--------+--------+--------+--------+
           |00001011|  0   8 |00100000|  0   2 |  0   2    0   7 |
           +--------+--------+--------+--------+--------+--------+

                      Integer  Length
                    +--------+--------+--------+--------+
                    |00100000|  0   2 |  0   0    4   7 |
                    +--------+--------+--------+--------+

           Field  data  element.   The specific field shown is the Text
      field with the contents "I will see you at lunch.":

             Field    Length    FID      ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   B |  0   4 |00000010|  1   8 |
           +--------+--------+--------+--------+--------+

                    +----                ----+
                    |I will see you at lunch.|
                    +----                ----+

                                     85

                                                             Appendix H

           Message containing four fields, Posted-Date, From, Text, and
      To.  It was sent on July 4, 1980 at 6 p.m. eastern daylight time.
      It  is  from  a person named Smith.  The text of the message is a
      question asking  the  recipient  "Are  you  going  to  watch  the
      fireworks?".  The message is sent to Jones:

            Message   Length    Type    Field    Length
           +--------+--------+--------+--------+--------+
           |01001101|  5   A |  0   1 |01001100|  1   9 |
           +--------+--------+--------+--------+--------+

                       FID      Date    Length   ASCII
                    +--------+--------+--------+--------+
                    |  0   2 |00101000|  1   6 |00000010|
                    +--------+--------+--------+--------+

                      Length
                    +--------+----            ----+
                    |  1   4 |19800704-180000-0400|
                    +--------+----            ----+

                      Field    Length    FID     ASCII
                    +--------+--------+--------+--------+
                    |01001100|  0   8 |  0   1 |00000010|
                    +--------+--------+--------+--------+

                      Length
                    +--------+-- --+
                    |  0   5 |Smith|
                    +--------+-- --+

                       Field   Length    FID     ASCII
                    +--------+--------+--------+--------+
                    |01001100|  2   8 |  0   4 |00000010|
                    +--------+--------+--------+--------+

                      Length
                    +--------+
                    |  2   5 |
                    +--------+

                    +----                             ----+
                    |Are you going to watch the fireworks?|
                    +----                             ----+

                      Field    Length    FID     ASCII
                    +--------+--------+--------+--------+
                    |01001100|  0   8 |  0   5 |00000010|
                    +--------+--------+--------+--------+

                                     86

                                                             Appendix H

                      Length
                    +--------+-- --+
                    |  0   5 |Jones|
                    +--------+-- --+

      H.3  Data Elements that Extend this Specification

           This  section  contains  examples  of  data elements used to
      extend this specification.  These data  elements  can  be  either
      primitives or constructors, depending on the extension.
           Extension  data  element  containing  a  length  code  and 3
      octets.  The octet immediately following the  length  code  iden-
      tifies it as Extension Data Element 7.  The Data Element Contents
      is  the final two octets.  The interpretation of the Data Element
      Contents would be defined in an extension or  successor  to  this
      message  format  specification.    [Note: this is an example. Any
      actual extension data element 7 (if it were ever used)  would  be
      completely different from anything done here.]:

           Extension  Length
           +--------+--------+--------+--------+--------+
           |01111110|  0   3 |  0   7 |  4   A    E   9 |
           +--------+--------+--------+--------+--------+

           Vendor-Defined  data  element containing a length code and 3
      octets.  The first octet identifies this as  vendor-defined  data
      element  number  114  (decimal), which this particular vendor has
      defined to  contain  three  printable  ASCII  characters  in  two
      octets.    (Data  element 114 (decimal) for another user would be
      completely different.  For example, it might contain  a  floating
      point number.):

              User    Length
           +--------+--------+--------+--------+--------+
           |01111111|  0   3 |  7   2 |   P    O    E   |
           +--------+--------+--------+--------+--------+

                                     87

                                                             Appendix H

      H.4  Fields

           This  section  contains  examples of Field data element con-
      structors for each of several different fields  (Keywords,  Text,
      Subject, Vendor-Defined).
           Field  data  element  for keywords .  The field contains two
      keywords, Message and Computer, each represented  in  a  separate
      ASCII-string data element.

              Field   Length  Keywords   ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   4 |  1   4 |00000010|  0   7 |
           +--------+--------+--------+--------+--------+

                    +--- ---+
                    |Message|
                    +--- ---+

                      ASCII    Length
                    +--------+--------+---  ---+
                    |00000010|  0   8 |Computer|
                    +--------+--------+---  ---+

                                     88

                                                             Appendix H

           Field  data  element  for  Text  with  a  Property-List data
      element containing a comment attached.  The text  field  contains
      the ASCII-String data element "Do you want lunch?"; the Property-
      List  data element contains a comment property, which consists of
      an ASCII-string data element containing "Now?":

             Field    Length   Text    Prop-List  Length
           +--------+--------+--------+--------+--------+
           |11001100|  2   0 |  0   4 |00100100|  0   9 |
           +--------+--------+--------+--------+--------+

                     Property  Length    PID     ASCII
                    +--------+--------+--------+--------+
                    |01000101|  0   7 |  0   1 |00000010|
                    +--------+--------+--------+--------+

                      Length
                    +--------+-  -+
                    |  0   4 |Now?|
                    +--------+-  -+

                      ASCII    Length
                    +--------+--------+----          ----+
                    |00000010|  1   2 |Do you want lunch?|
                    +--------+--------+----          ----+

           Field data element for Subject  containing  an  ASCII-String
      data  element  ("Good  restaurants  in  Detroit"  followed  by  a
      carriage return and a line feed).  (A recipient would expect  the
      message  to  contain  some  information  about restaurants in the
      Detroit area.):

             Field    Length   Subject   ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  2   1 |  0   7 |00000010|  1   E |
           +--------+--------+--------+--------+--------+

                    +----                            ----+
                    |Good restaurants in Detroit.<cr><lf>|
                    +----                            ----+

                                     89

                                                             Appendix H

           Field  data  element whose form and meaning was defined by a
      vendor.    This  vendor  has  defined  vendor-defined  field   12
      (decimal)  to  be  a field with a printing name of "Reply-by" and
      contents consisting of a date; January  7,  1981  in  this  case.
      (The  meaning of vendor-defined field 12 is unique to the vendor;
      the same field number would  have  different  meaning  for  other
      vendors.):

             Field    Length  Qualifier   User   number
           +--------+--------+--------+--------+--------+
           |11001100|  1   F |  8   2 |  0   0    0   C |
           +--------+--------+--------+--------+--------+

                     Prop-List Length  Property  Length
                    +--------+--------+--------+--------+
                    |00100100|  0   E |01000101|  0   C |
                    +--------+--------+--------+--------+

                        PID    ASCII    Length
                    +--------+--------+--------+---- ----+
                    |  0   2 |00000010|  0   9 |Reply-By:|
                    +--------+--------+--------+---- ----+

                       Date    Length   ASCII    Length
                    +--------+--------+--------+--------+
                    |00101000|  0   A |00000010|  0   8 |
                    +--------+--------+--------+--------+

               +---  ---+
                    |19810107|
                    +---  ---+

      H.5  Messages

           This  section contains several examples of complete messages
      and shows the results of  reissuing  a  message.    (See  Section
      3.2.2.)

                                     90

                                                             Appendix H

           The  following  sample message had Stevens as its originator
      and Johnson as its recipient.  The message was sent on August 14,
      1980 at 10 a.m. EDT.  The subject  of  the  message  is  "Project
      Deadline"  and the message is a reminder that the deadline is the
      next day and that the section of the report for the project being
      done by Johnson should be turned in to Stevens  by  3  p.m.  that
      day.

            Message       Length         Type
           +--------+--------+--------+--------+
           |01001101|  8   1 |  B   6 |  0   1 |
           +--------+--------+--------+--------+

              Field   Length    FID     ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   5 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Johnson|
                    +--------+--- ---+

             Field    Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   1 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Stevens|
                    +--------+--- ---+

             Field    Length    FID     ASCII    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   3 |  0   7 |00000010|  1   0 |
           +--------+--------+--------+--------+--------+

                    +----        ----+
                    |Project Deadline|
                    +----        ----+

             Field    Length    FID      Date    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   7 |  0   2 |00101000|  1   4 |
           +--------+--------+--------+--------+--------+

                                     91

                                                             Appendix H

                      ASCII    Length
                    +--------+--------+----          ----+
                    |00000010|  1   2 |19800814-1000-0400|
                    +--------+--------+----          ----+

             Field    Length    FID      ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  6   D |  0   4 |00000010|  6   A |
           +--------+--------+--------+--------+--------+

                    +----
                    |Don't forget the project report is
                    +----

                     due tomorrow.  Please have<CrLf>

                     your section to me by three this

                           ----+
                     afternoon.|
                           ----+

           The  following  example illustrates the results of reissuing
      the first message in this section.   This  message  contains  the
      original  message  (as  a  Message  data  element), To, From, and
      Posted-Date fields, and a Reissue-Type field  with  Redistributed
      as its value:

            Message       Length         Type
           +--------+--------+--------+--------+
           |01001101|  8   1 |  F   C |  0   1 |
           +--------+--------+--------+--------+

              Field   Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   9 |  0   5 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--  --+
                    |  0   6 |Cooper|
                    +--------+--  --+

                                     92

                                                             Appendix H

             Field    Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   1 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Johnson|
                    +--------+--- ---+

             Field    Length    FID      Date    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   7 |  0   2 |00101000|  1   4 |
           +--------+--------+--------+--------+--------+

                       ASCII   Length
                    +--------+--------+----          ----+
                    |00000010|  1   2 |19800814-1030-0400|
                    +--------+--------+----          ----+

             Field    Length    FID      ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   0 |  2   5 |00000010|  0   D |
           +--------+--------+--------+--------+--------+

                    +----     ----+
                    |Redistributed|
                    +----     ----+

            Message       Length         Type
           +--------+--------+--------+--------+
           |01001101|  8   1 |  B   6 |  0   1 |
           +--------+--------+--------+--------+

              Field   Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   5 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Johnson|
                    +--------+--- ---+

             Field    Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   1 |00000010|
           +--------+--------+--------+--------+

                                     93

                                                             Appendix H

                      Length
                    +--------+--- ---+
                    |  0   7 |Stevens|
                    +--------+--- ---+

             Field    Length    FID     ASCII    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   3 |  0   7 |00000010|  1   0 |
           +--------+--------+--------+--------+--------+

                    +----        ----+
                    |Project Deadline|
                    +----        ----+

             Field    Length    FID      Date    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   7 |  0   2 |00101000|  1   4 |
           +--------+--------+--------+--------+--------+

                      ASCII    Length
                    +--------+--------+----          ----+
                    |00000010|  1   2 |19800814-1000-0400|
                    +--------+--------+----          ----+

             Field    Length    FID      ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  6   D |  0   4 |00000010|  6   A |
           +--------+--------+--------+--------+--------+

                    +----
                    |Don't forget the project report is
                    +----

                     due tomorrow.  Please have<CrLf>

                     your section to me by three this

                           ----+
                     afternoon.|
                           ----+

      H.6  Unknown Lengths

           This  section contains two examples of data elements with an
      unknown length.  The two examples have been presented in sections
      H.2 and H.5, but with a known rather than an unknown length.

                                     94

                                                             Appendix H

           Set  data  element  with  an  unknown  length containing two
      Integer data elements.  The first integer  has  a  value  of  519
      (decimal)  while the value of the second is 71 (decimal).  (These
      two values have no ordering because they belong to a set.)

              Set     Length   Integer  Length
           +--------+--------+--------+--------+--------+--------+
           |00001011|  8   0 |00100000|  0   2 |  0   2    0   7 |
           +--------+--------+--------+--------+--------+--------+

                      Integer  Length
                    +--------+--------+--------+--------+
                    |00100000|  0   2 |  0   0    4   7 |
                    +--------+--------+--------+--------+

                    End-of-Con Length
                    +--------+--------+
                    |00000000|00000000|
                    +--------+--------+

           The following sample message  with  an  unknown  length  had
      Stevens  as  its  originator  and  Johnson as its recipient.  The
      message was sent on August 14, 1980 at 10 a.m. EDT.  The  subject
      of  the  message  is  "Project  Deadline"  and  the  message is a
      reminder that the deadline is the next day and that  the  section
      of  the  report  for  the project being done by Johnson should be
      turned in to Stevens by 3 p.m. that day.

            Message   Length    Type
           +--------+--------+--------+
           |01001101|  8   0 |  0   1 |
           +--------+--------+--------+

              Field   Length    FID     ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   5 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Johnson|
                    +--------+--- ---+

                                     95

                                                             Appendix H

             Field    Length    FID      ASCII
           +--------+--------+--------+--------+
           |01001100|  0   A |  0   1 |00000010|
           +--------+--------+--------+--------+

                      Length
                    +--------+--- ---+
                    |  0   7 |Stevens|
                    +--------+--- ---+

             Field    Length    FID     ASCII    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   3 |  0   7 |00000010|  1   0 |
           +--------+--------+--------+--------+--------+

                    +----        ----+
                    |Project Deadline|
                    +----        ----+

             Field    Length    FID      Date    Length
           +--------+--------+--------+--------+--------+
           |01001100|  1   7 |  0   2 |00101000|  1   4 |
           +--------+--------+--------+--------+--------+

                      ASCII    Length
                    +--------+--------+----          ----+
                    |00000010|  1   2 |19800814-1000-0400|
                    +--------+--------+----          ----+

             Field    Length    FID      ASCII   Length
           +--------+--------+--------+--------+--------+
           |01001100|  6   D |  0   4 |00000010|  6   A |
           +--------+--------+--------+--------+--------+

                    +----
                    |Don't forget the project report is
                    +----

                     due tomorrow.  Please have<CrLf>

                     your section to me by three this

                           ----+
                     afternoon.|
                           ----+

                    End-of-Con Length
                    +--------+--------+
                    |00000000|00000000|
                    +--------+--------+

                                     96

                                                             Appendix H

      H.7  Message Encoding Using Vendor-Defined Fields

           This  example is provided to illustrate the encoding of non-
      FIPS format messages in the FIPS format.  It is the intent of the
      standard to deal with computer based message  systems  which  are
      primarily  intended for person-to-person use.  This example deals
      with the definition and use of vendor-defined  fields  to  extend
      the  use  of  the  standard to station-to-station messaging.  The
      context is a military message using the military standard  JANAP-
      128 format.

      H.7.1  Example of a JANAP-128 Message

          JANAP-128
          RTTUZYUW RUABCDE0010 0330930-UUUU--RUXABYE.
          ZNR UUUUU
          R 020830Z FEB 82
          FM Commander,Atlantic Fleet
          TO USS SHIPA
          BT
          UNCLAS

           MESSAGE        BODY

          BT
          #0010
          NNNN

      H.7.2  Encoding of Example using the FIPS Message Format

            Message   Length             Type
           +--------+--------+--------+--------+
           |01001101|  8   1 |  D   0 |  0   1 |
           +--------+--------+--------+--------+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   4 |  1   8 |
                    +--------+--------+--------+

                                     97

                                                             Appendix H

                               ASCII    Length
                             +--------+--------+--------+
                             |00000010|  0   1 |    R   |
                             +--------+--------+--------+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   7 |  8   2 |  0   0 |  0   1 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+--------+--------+
                             |00000010|  0   2 |    T   |    T   |
                             +--------+--------+--------+--------+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   6 |  8   2 |  0   0 |  0   2 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+--------+
                             |00000010|  0   1 |    U   |
                             +--------+--------+--------+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   9 |  8   2 |  0   0 |  0   3 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   4 |   ZYUW   |
                             +--------+--------+----  ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   A |  2   2 |
                    +--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----   ----+
                             |00000010|  0   7 |  RUABCDE  |
                             +--------+--------+----   ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   7 |  1   7 |
                    +--------+--------+--------+

                                     98

                                                             Appendix H

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   4 |   0010   |
                             +--------+--------+----  ----+

                      Field    Length    FID      Date    Length
                    +--------+--------+--------+--------+--------+
                    |01001100|  1   8 |  0   2 |00101000|  1   5 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----           ----+
                             |00000010|  1   3 |19820202093000-0000|
                             +--------+--------+----           ----+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   9 |  8   2 |  0   0 |  0   2 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   4 |   UUUU   |
                             +--------+--------+----  ----+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   C |  8   2 |  0   0 |  0   4 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   7 |  RUXABYE |
                             +--------+--------+----  ----+

                      Field    Length    FID
                    +--------+--------+--------+--------+--------+
                    |01001100|  0   A |  8   2 |  0   0 |  0   2 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----   ----+
                             |00000010|  0   5 |   UUUUU   |
                             +--------+--------+----   ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   4 |  1   8 |
                    +--------+--------+--------+

                                     99

                                                             Appendix H

                               ASCII    Length
                             +--------+--------+--------+
                             |00000010|  0   1 |    R   |
                             +--------+--------+--------+

                      Field    Length    FID      Date    Length
                    +--------+--------+--------+--------+--------+
                    |01001100|  1   4 |  1   1 |00101000|  1   1 |
                    +--------+--------+--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----       ----+
                             |00000010|  0   F |8202020830-0000|
                             +--------+--------+----       ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  1   B |  0   1 |
                    +--------+--------+--------+

                               ASCII    Length
                             +--------+--------+
                             |00000010|  1   8 |
                             +--------+--------+

                                      +----                ----+
                                      |Commander,Atlantic Fleet|
                                      +----                ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   C |  0   5 |
                    +--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----   ----+
                             |00000010|  0   9 | USS SHIPA |
                             +--------+--------+----   ----+

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   7 |  0   4 |
                    +--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   4 |   BODY   |
                             +--------+--------+----  ----+

                                     100

                                                             Appendix H

                      Field    Length    FID
                    +--------+--------+--------+
                    |01001100|  0   7 |  1   7 |
                    +--------+--------+--------+

                               ASCII    Length
                             +--------+--------+----  ----+
                             |00000010|  0   4 |   0010   |
                             +--------+--------+----  ----+

      H.7.3  Field Mappings of JANAP-128 to FIPS Format

          JANAP-128 Field              FIPS Format Field

          Precedence                   Precedence (Appendix A)
          Language Media Format        Vendor-Defined
          Security                     Vendor-Defined
          Content Indicator Code       Vendor-Defined
          Origination Station          Sender (Appendix A)
            Routing Indication
          Station Serial Number        Originator-Serial-Number
                                         (Appendix A)
          Time of File                 Posted-Date (Appendix A)
          Security                     Vendor-Defined
          Destination Station          Vendor-Defined
            Routing Indicator
          Security                     Vendor-Defined
          Precedence                   Precedence (Appendix A)
          Date/Time Group              Date (Appendix A)
          FM                           From (Appendix A)
          TO                           To (Appendix A)
          Body of Message              Text (Appendix A)
          Station Serial Number        Originator-Serial-Number
                                         (Appendix A)

      H.7.4  Vendor-Defined Fields

                                     101

      -----------------------------------------------------------------

           Field Name                                Identifier Value  
                                                                     8

                                 Description

      -----------------------------------------------------------------

           Language Media Format                                    01 
                                                                      8
           This   field   contains  two  ASCII  characters;  the  first
      indicates the input media and the second the output media.

           Security                                                 02 
                                                                      8
           This  field  contains  a  variable  length  ASCII  character
      indicator of the security classification of the messages.

           Content Indicator Code                                   03 
                                                                      8
           This  field  contains  four  ASCII  characters  and provides
      information describing the message content and  message  handling
      actions to be performed.

           Destination Station Routing Indicator                    04 
                                                                      8
           This field contains four ASCII characters indicating the CPU
      and terminal device to which the message should be sent.

                                     102

                                 REFERENCES

      [BlaR-80]
           R. P. Blanc and J. F. Heafner. The NBS Program in Computer
           Network Protocol Standards. In Proceedings, ICCC 80.  1980.

      [CCIT-82]
           CCITT Study Group VII/5. Draft recommendation X.MHS1:
           Message Handling Systems: System Model - Service Elements
           (Version 2). Technical Report, International Telegraph and
           Telephone Consultative Committee (CCITT), December, 1982.

      [CroD-77]
           David H. Crocker, John J. Vittal, Kenneth T. Pogran,
           D. Austin Henderson, Jr. Standard for the Format of ARPA
           Network Text Messages. RFC 733, The Rand Corporation, Bolt
           Beranek and Newman Inc, Massachussets Institute of
           Technology, Bolt Beranek and Newman Inc., November, 1977.

      [FeiE-79]
           E. Feinler, J. Pickens, and A. Sjoberg. Computer Message
           Services Bibliography. Technical Report NIC-BIBLIO-791201,
           SRI International, December, 1979.

      [ISOD-79]
           ISO/TC97/SC6 Data Communications. Second Draft Proposed
           Communication Heading Format Standard. ISO/TC97/SC6 N 1948,
           ISO International Organization for Standardization
           Organization Internationale de Normalisation, September,
           1979. Secretariat: USA (ANSI).

      [ISOD-82]
           ISO/TC97/SC16. Information Processing Systems - Open Systems
           Interconnection - Basic Reference Model. ISO/DIS 7498, ISO
           International Organization for Standardization Organization
           Internationale de Normalisation, December, 1982.

      [NatB-68]
           National Bureau of Standards. Calendar Date. Federal
           Information Processing Standards Publication 4, U.S.
           Department of Commerce / National Bureau of Standards,
           November, 1968.

      [NatB-75]
           National Bureau of Standards. Code Extension Techniques in 7
           or 8 Bits. Federal Information Processing Standards
           Publication 35, U.S. Department of Commerce / National
           Bureau of Standards, June, 1975.

                                     103

      [NatB-77]
           National Bureau of Standards. Data Encryption Standard.
           Federal Information Processing Standards Publication 46,
           U.S. Department of Commerce / National Bureau of Standards,
           January, 1977.

      [NatB-79a]
           National Bureau of Standards. Representations of Local Time
           of the Day for Information Interchange. Federal Information
           Processing Standards Publication 58, U.S. Department of
           Commerce / National Bureau of Standards, February, 1979.

      [NatB-79b]
           National Bureau of Standards. Representations of Universal
           Time, Local Time Differentials, and United States Time Zone
           References for Information Interchange. Federal Information
           Processing Standards Publication 59, U.S. Department of
           Commerce / National Bureau of Standards, February, 1979.

      [NatB-80]
           National Bureau of Standards. Code for Information
           Interchange. Federal Information Processing Standards
           Publication 1-1, U.S. Department of Commerce / National
           Bureau of Standards, December, 1980.

      [PosJ-79]
           Jonathan B. Postel. INTERNET MESSAGE PROTOCOL. RFC 753,
           Information Sciences Institute, March, 1979.

      [TasG-80]
           Task Group X3S33 on Data Communications Formats, ANSI
           Subcommittee X3S3 on Data Communications. Third Draft
           Proposed American National Standard for Heading Format
           Structure for Code Independent Communication Headings. ANSI
           document X3S37/80-01, Computer and Business Equipment
           Manufacturers Association, 1980.

                                     104

                                    INDEX

                ASCII-String   35, 36, 47, 50, 52, 54, 58, 59, 60, 61,
                        63, 65, 69
                Assignment   22, 28, 61
                Attachments   23, 57
                Author   19, 57

                BASIC   18
                BASIC Data Elements
                   ASCII-String   47, 63
                   Date   50, 65
                   End-of-Constructor   48, 66
                   Field   50, 66
                   Message   51, 67
                BASIC fields
                   Cc   20
                   Reply-To   19
                   Subject   23
                   Text   23
                BASIC syntactic elements   35
                Bcc   19, 25, 57
                Bit numbering in octets   37
                Bit-String   36, 42, 47, 49, 50, 52, 64, 65, 69
                Boolean   36, 48, 64

                Cc   20, 58
                Chains of correspondence   29
                Circulate-Next   20, 31, 58
                Circulate-To   20, 31, 58
                Circulation   31
                Comment   36, 37, 44, 54
                Comments   23, 58
                Compliance requirements   41
                Compressed   37, 43, 49, 54, 65
                Compression identifier   49, 65
                Compression Identifiers
                   Unspecified   54
                Constructor data element   35, 36
                Contents   38, 76
                Cross Referencing   29

                Data Element Contents   43, 44, 87, 42, 44, 52, 69, 42,
                        44, 46, 47, 51, 64, 69, 87
                Data Elements
                   ASCII-String (BASIC)   47, 63
                   Bit-String (OPTIONAL)   47, 64

                                     105

                   Boolean (OPTIONAL)   48, 64
                   Compressed (OPTIONAL)   49, 65
                   Date (BASIC)   50, 65
                   Encrypted (OPTIONAL)   50, 65
                   End-of-Constructor (BASIC)   48, 66
                   Extension (OPTIONAL)   52, 66
                   Field (BASIC)   50, 66
                   Integer (OPTIONAL)   48, 67
                   Message (BASIC)   51, 67
                   No-Op (OPTIONAL)   49, 67
                   Padding (OPTIONAL)   49, 68
                   Property (OPTIONAL)   51, 68
                   Property-List (OPTIONAL)   51, 68
                   Sequence (OPTIONAL)   51, 69
                   Set (OPTIONAL)   52, 69
                   Unique-ID (OPTIONAL)   52, 69
                   Vendor-Defined (OPTIONAL)   53, 70
                Date   20, 50, 58, 60, 61, 62, 65
                Dating   30
                Delivery   13, 20, 60
                Delivery Protocol   13
                Delivery Slot   13

                Encapsulating   26
                Encrypted   37, 43, 50, 54, 65
                Encryption identifier   50, 65
                Encryption Identifiers
                   FIPS-Standard   54
                   Unspecified   54
                End-Date   20, 21, 30, 58, 62
                End-Of-Constructor   36, 42, 44, 48, 66
                Extension   35, 46, 52, 66

                Field   14, 31, 35, 36, 37, 43, 50, 51, 66, 67, 72
                Field Identifier   50, 66
                Field label presentation   35
                Fields
                   Attachments (OPTIONAL)   57, 23
                   Author (OPTIONAL)   57, 19
                   Bcc (OPTIONAL)   57, 19
                   Cc (BASIC)   58, 20
                   Circulate-Next (OPTIONAL)   58, 20
                   Circulate-To (OPTIONAL)   58, 20
                   Comments (OPTIONAL)   58, 23
                   Date (OPTIONAL)   58, 20
                   End-Date (OPTIONAL)   58, 20
                   From (REQUIRED)   59, 19
                   In-Reply-To (OPTIONAL)   59, 21
                   Keywords (OPTIONAL)   59, 23
                   Message-Class (OPTIONAL)   59, 22
                   Message-ID (OPTIONAL)   59, 21

                                     106

                   Obsoletes (OPTIONAL)   59, 21
                   Originator-Serial-Number (OPTIONAL)   59, 21
                   Posted-Date (REQUIRED)   60, 20
                   Precedence (OPTIONAL)   60, 22
                   Received-Date (OPTIONAL)   60, 20
                   Received-From (OPTIONAL)   60, 22
                   References (OPTIONAL)   60, 22
                   Reissue-Type (OPTIONAL)   61, 22
                   Reply-To (BASIC)   61, 19
                   Sender (OPTIONAL)   61, 19
                   Start-Date (OPTIONAL)   61, 21
                   Subject (BASIC)   61, 23
                   Text (BASIC)   61, 23
                   To (REQUIRED)   61, 19
                   Warning-Date (OPTIONAL)   62, 21
                FIPS-Standard   54, 55
                From   17, 19, 29, 57, 59, 61

                Globally unique identifiers   29

                Identifier octet   38, 41, 37, 38, 42, 44, 76
                Identifiers
                   globally unique   29
                In-Reply-To   21, 29, 59
                Indefinite length code   41
                Integer   36, 48, 52, 67, 69

                Keywords   23, 59, 88

                Length Code   40, 41, 42, 38, 39, 40, 41, 42, 44, 46,
                        76, 77, 87
                Long length code   41

                Message Transfer System   13, 22, 60
                Message   14, 17, 35, 36, 37, 43, 51, 67
                Message content   13
                Message envelope   13
                Message stores   30
                Message Transfer System   13, 22, 60, 12, 13, 14, 17,
                        20, 22, 60
                Message Types
                   FIPS-Standard   55
                Message-Class   22, 59
                Message-ID   21, 22, 29, 31, 59, 60

                No-Op   49, 67
                Numbering bits in octets   37

                Obsoletes   21, 29, 59
                Octets
                   bit numbering in   37

                                     107

                OPTIONAL   18
                OPTIONAL Data Elements
                   Bit-String   47, 64
                   Boolean   48, 64
                   Compressed   49, 65
                   Encrypted   50, 65
                   Extension   52, 66
                   Integer   48, 67
                   No-Op   49, 67
                   Padding   49, 68
                   Property   51, 68
                   Property-List   51, 68
                   Sequence   51, 69
                   Set   52, 69
                   Unique-ID   52, 69
                   Vendor-Defined   53, 70
                OPTIONAL fields
                   Attachments   23
                   Author   19
                   Bcc   19
                   Circulate-Next   20
                   Circulate-To   20
                   Comments   23
                   Date   20
                   End-Date   20
                   In-Reply-To   21
                   Keywords   23
                   Message-Class   22
                   Message-ID   21
                   Obsoletes   21
                   Originator-Serial-Number   21
                   Precedence   22
                   Received-Date   20
                   Received-From   22
                   References   22
                   Reissue-Type   22
                   Sender   19
                   Start-Date   21
                   Warning-Date   21
                OPTIONAL syntactic elements   35
                Originator   15, 18, 20, 30, 57, 58, 59, 61
                Originator-Serial-Number   21, 30, 59

                Padding   49, 68
                Person   18
                Posted-Date   17, 20, 31, 58, 60
                Posting   13
                Posting Protocol   13
                Posting Slot   13
                Precedence   22, 60
                Precedence categories   22

                                     108

                Precedence scheme   60
                Presentation
                   field label   35
                Primitive data element   36, 35, 36
                Printing-Name   36, 37, 44, 54, 82
                Process   18
                Properties
                   Comment   54
                   Printing-Name   54
                Property   38, 43, 51, 68
                Property-Identifier   51, 68
                Property-List   36, 38, 44, 46, 51, 68, 76

                Qualifier   38, 39, 40, 41, 42, 43, 44, 46, 47, 49, 50,
                        51, 52, 53, 64, 65, 66, 68, 70, 76
                Qualifiers   43

                Received-Date   20, 60
                Received-From   22, 60
                Recipient   15, 19, 20, 22, 57, 58, 60, 61
                Redistribution   22, 26, 61
                References   22, 29, 60
                Reissue-Type   22, 61
                Reply   18, 28
                Reply-to   19, 28, 59, 61
                REQUIRED   18
                REQUIRED fields
                   From   19
                   Posted-Date   20
                   To   19
                Requirements
                   compliance   41
                Role   18

                Sender   19, 31, 61
                Sequence   35, 36, 51, 69
                Sequences   36
                Serial Numbers   21, 30, 59
                Set   36, 51, 52, 69
                Short length code   41
                Slot   13
                Start-Date   21, 30, 61
                Subject   23, 61
                Syntactic reissuing   26

                Text   23, 32, 61
                To   17, 19, 31, 37, 61

                Unique identifiers   29
                Unique-ID   52, 59, 60, 69
                Unspecified   54

                                     109

                User Agent   12, 13, 14
                User interface   35

                Vendor-Defined   35, 46, 53, 70

                Warning-Date   21, 30, 62

                                     110

 

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