FIPA Agent Message Transport Protocol
for IIOP Specification


Document title

FIPA Agent Message Transport Protocol for IIOP Specification

Document number


Document source

FIPA Agent Management

Document status


Date of this status





Change history


Separated out from specification OC00024


Made ready for Experimental status


FAB editorial and consistency changes; Approved for Experimental


Modified the IDL interface with the new Envelope structured type









© 2000 Foundation for Intelligent Physical Agents -

Geneva, Switzerland


Use of the technologies described in this specification may infringe patents, copyrights or other intellectual property rights of FIPA Members and non-members. Nothing in this specification should be construed as granting permission to use any of the technologies described. Anyone planning to make use of technology covered by the intellectual property rights of others should first obtain permission from the holder(s) of the rights. FIPA strongly encourages anyone implementing  any part of this specification to determine first whether part(s) sought to be implemented are covered by the intellectual property of others, and, if so, to obtain appropriate licenses or other permission from the holder(s) of such intellectual property prior to implementation. This specification is subject to change without notice. Neither FIPA nor any of its Members accept any responsibility whatsoever for damages or liability, direct or consequential, which may result from the use of this specification.


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1     Scope. 1

2     Message Transport Protocol for IIOP. 2

2.1      Component Name. 2

2.2      Interface Definition. 2

2.3      ACC Processing of IDL Envelope. 2

2.4      Concrete Message Envelope Syntax. 3

3     References. 5

1         Scope

This document is part of the FIPA specifications and deals with message transportation between inter-operating agents. This document also forms part of the FIPA Agent Management Specification [FIPA00023] and contains specifications for:


·         The transportation of messages between agents using the Internet Inter-Orb Protocol (IIOP - see [OMGiiop]).

2         Message Transport Protocol for IIOP

This MTP is based on the transfer of an OMG IDL structure containing the message envelope and an octet sequence representing the ACL message body. The envelope and the message body are transferred together within a single IIOP one-way invocation [OMGiiop].


Once the request has been received, the message envelope is used by the ACC to obtain the instructions and information needed to correctly handle the message body.


2.1        Component Name

The name assigned to this component is:




2.2        Interface Definition

The following IDL specifies the message transport interface. This interface contains a single operation message() that requires a single argument. This argument has two attributes: a sequence of Envelope structures holding the message envelope, and the payload, that is a sequence of octets containing the ACL message body.


module FIPA {

  typedef sequence<Envelope> Envelopes;

  typedef sequence<octet> Payload;

  struct FipaMessage {

    Envelopes messageEnvelopes;

    Payload   messageBody;



  interface MTS {

    oneway void message(in FipaMessage aFipaMessage);




2.3        ACC Processing of IDL Envelope 

According to [FIPA00067], a FIPA compliant ACC is not allowed to modify any element of the envelope that it receives. It is however allowed to update a value in one of the envelope slots by adding a new Envelope element at the end of the messageEnvelopes sequence. This new element is required to have only those slot values that the ACC wishes to add or update plus a new ReceivedObject element as mandated in [FIPA00067].


As a consequence, an ACC that receives a message must implement the procedure described in the following pseudo-code. The procedure recomposes the full envelope structure with its latest values for each slot. The procedure simply shows that the ACC starts from the last envelope in the sequence and continues until it has all the required values for each slot of the envelope.


EnvelopeWithAllFields := new empty Envelope;


while ( (EnvelopeWithAllFields does not contain values for all its fields)

        OR (all Envelopes in the sequence have been processed) ) {

 // the ACC gets the next envelope in the sequence starting from the end

 tempEnvelope = getNextEnvelope; 

 foreach field in an envelope {

   if ((this field has no value in envelopeWithAllFields)

       AND (this field has a value in tempEnvelope))

   then copy the value of this field from tempEnvelope to envelopeWithAllFields




EnvelopeWithAllFields now contains the latest values for all its fields.


For example:



  to = tizio

  from = caio

  aclRepresentation = XML

  received = …


Envelope (1):

  from =

  received = …


Envelope (2) :

  intended-receiver =

  received = …



 to = tizio                                (from envelope 0)

 from =                   (from envelope 1)

 intended-receiver =   (from envelope 2)

 date = 25 May 2000                        (from envelope 0)


2.4        Concrete Message Envelope Syntax

The Abstract Envelope Syntax from [FIPA00067] maps into a set of OMG IDL structured types, all of which are enclosed within the FIPA module.


The following standard convention applies for the identification of optional slots: an empty string and an empty sequence identify the non-presence of a slot.


The complete IDL definition is:


module FIPA {

  // No need for an URL struct, since it's only put in the

  // message envelope for informational purposes.

  typedef string URL;


  typedef sequence<string> strings; // a sequence of strings


  // this generic type is used to represent user-defined, non FIPA-defined,

  // properties that are added to the message envelope in the form of a

  // keyword and value pair.

  struct Property {

    string keyword;

    any value;



  struct AgentID {  // Agent Identifier

    string name;

    sequence<AgentID>  addresses;

    sequence<AgentID>  resolvers;

    sequence<Property> userDefinedProperties;



  typedef sequence<AgentID> AgentIDs;  // sequence of Agent Identifiers


  // IDL struct to represent a time stamp.

  // It is based on the ISO8601 format with extension for millisecond durations.

  // The value of the typeDesignator must be a valid

  // AlphaCharacter, i.e. ['a'-'z' , 'A'-'Z'], that identifies the timezone.

  // ISO8601 reports the mapping between typeDesignator and timezone.

  // The typeDesignator for UTC is the character 'Z'.

  // If the value of typeDesignator is not an AlphaCharacter, it defaults

  // to the local timezone.

  struct DateTime {

    short year;  // year (e.g. 2000)

    short month; // between 1 and 12

    short day;   // between 1 and 31

    short hour;  // between 0 and 23

    short minutes; // between 0 and 59

    short seconds; // between 0 and 59

    short milliseconds; // between 0 and 999        

    char  typeDesignator; // see comment above



  struct ReceivedObject {

    URL by;

    URL from;

    DateTime date;

    string id;

    string via;



  typedef  sequence<Property> TransportBehaviourType;


  struct Envelope {

    AgentIDs               to;

    AgentID                from;

    string                 comments;

    string                 aclRepresentation;

    long                   payloadLength;

    string                 payloadEncoding;

    DateTime               date;

    strings                encrypted;

    AgentIDs               intendedReceiver;

    ReceivedObject         received;

    TransportBehaviourType transportBehaviour;

    sequence<Property>     userDefinedProperties; // user-defined properties



  typedef sequence<Envelope> Envelopes;


  typedef sequence<octet> Payload;


  struct FipaMessage {

    Envelopes messageEnvelopes;

    Payload   messageBody;



  interface MTS {

    oneway void message(in FipaMessage aFipaMessage);




3         References

[FIPA00023]      FIPA Agent Management Specification. Foundation for Intelligent Physical Agents, 2000.

[FIPA00067]      FIPA Agent Message Transport Service Specification. Foundation for Intelligent Physical Agents, 2000.

[OMGiiop]         OMG Internet Inter-ORB Protocol Specification, Common Object Request Broker Architecture 2.2. Object Management Group, 1999.