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Exception Handling in Goal-
Oriented Multi-Agent Systems

İbrahim Çakırlar, Erdem Eser Ekinci and
Oğuz Dikenelli
Ege University Computer Engineering Department
İzmir, Turkiye
                                                2




                 Overview

• Introduction
• Exception Handling Mechanism for Goal
  Oriented MASs
• Abstact Exception Handling Architecture for
  MASs
• Our Implementation
• Case Study : Electronic Barter Application
• Other Exception Handling Approaches
• Conclusion
                                                     3




                Introduction

• Exception handling is based on the exception
  concept that is defined in software systems such
  as an error occurred during execution flow of a
  program.

• Traditional technologies like Object Oriented
  Programming(OOP) try to satisfy reliability and
  robustness properties via exception handling.
                                                    4


                Introduction

• Classical exception handling techniques can not
  be applied to MASs for the reason of some
  properties:
 ▫   cooperative,
 ▫   autonomy,
 ▫   open,
 ▫   distributed.

• In this research we design a specialized exception
  handling approach for MASs.
                                                     5


• Introduction

• Exception Handling Mechanism for Goal
  Oriented MASs

• Abstact Exception Handling Architecture for MASs

• Our Implementation

• Other Exception Handling Approaches

• Case Study : Electronic Barter Application

• Conclusion
                                                                                6


 Exception Handling Mechanism for
 Goal-oriented Multi-agent Systems
• In many cases and researches exception handling is
  considered as a later step of development process.

• Lamsweerde and Letier* also claim using goals to
  model exception handlers at the requirement
  analysis phase of goal-oriented MAS development.


*Axel van Lamsweerde and Emmanuel Letier. Handling obstacles in goal-oriented
  requirements engineering. Software Engineering, 26(10) :9781005, 2000
                                    7


Exception Handling Mechanism for
Goal-oriented Multi-agent Systems
                                                    8


Exception Handling Mechanism for
Goal-oriented Multi-agent Systems

• Goal-oriented multi-agent system executable
  entities : system goal, agent goal, plan.


• In MASs, execution flow designed with the terms
  of cooperation and standalone.
                                                                             9


Exception Handling Mechanism for
Goal-oriented Multi-agent Systems
• We propose a layered exception hierarchy like
  Platon*.

• Exception levels
  ▫ Multi-Agent Level
  ▫ Agent Level
  ▫ Plan Level

* Eric Platon, Nicolas Sabouret, and Shinichi Honiden. An architecture for
  exception management in multi-agent systems. International Journal on
  Agent-Oriented Software Engineering, 2008
                                                         10


Exception Handling Mechanism for
Goal-oriented Multi-agent Systems
• We categorized exception levels due to hierarchy
  of executable entities.

  Exception
                  Entity      Standalone   Cooperative
    Level

  MAS Level     System Goal


  Agent Level   Agent Goal


   Plan Level      Plan
                                                                        11


 Exception Handling Mechanism for
 Goal-oriented Multi-agent Systems
• In our principle, conveniently with the
  simplicity principle of Goodenough*, claim that
  each exception should be handled with the
  executable entities that are same level with the
  exception occurred in.

• If it can not be handled in the same level, it
  hampers the execution flow of one upper level.
  So,it should be handled in the upper level.

* John B. Goodenough. Exception handling design issues. SIGPLAN Not.,
   10(7):41 -45, 1975
                                    12


Exception Handling Mechanism for
Goal-oriented Multi-agent Systems
                                                   13


• Introduction

• Exception Handling Mechanism for Goal Oriented
  MASs

• Abstact Exception Handling Architecture for
  MASs

• Our Implementation

• Case Study : Electronic Barter Application

• Other Exception Handling Approaches

• Conclusion
                                                   14


      Abstract Exception Handling
         Architecture of MASs
• Three phase of agent cyclic execution model;
  perception, reasoning and action.

• As other operations exception handling spreads
  over the same execution model.

• Perception phase à Reasoning Phase à Action
  Phase
                                                    15


         Abstract Exception Handling
            Architecture of MASs

• Perception phase: Perception of exceptional/
  unexpected situation.

• Reasoning phase: Decide exception cause, occurance
  level and handling level

• Action phase : Apply decided exception handling
  policy
                                                     16



• Introduction

• Exception Handling Mechanism for Goal Oriented
  MASs

• Abstact Exception Handling Architecture for MASs

• Our Implementation

• Case Study : Electronic Barter Application

• Other Exception Handling Approaches

• Conclusion
                                                    17




          Our Implementation

• Our abstract exception handling architecture is
  implemented in SEAGENT Multi-Agent
  Development Framework.

• The primitive properties of SEAGENT are
  semantic web enability, goal orientation and
  HTN based plan execution.
                                        18


 Our Implementation - Decision making
               Cycle
    exceptions are
AllPlan Level is
occur in this step.
   handled in this
  step. But for other
  levels the cycle
  goes on.
                                                19


         Our Implementation – Execution
Goal                Sample
Model




 Plan
 Model
                                   Dynamically
                                   added when an
                                   exception occurs
                                                     20


• Introduction

• Exception Handling Mechanism for Goal Oriented
  MASs

• Abstact Exception Handling Architecture for MASs

• Our Implementation

• Case Study : Electronic Barter Application

• Other Exception Handling Approaches

• Conclusion
                                                                     21



Case Study : Electronic Barter Application
 Customer
  Agent1
                                 Barter
                               Management     Notify for
                                 Agent                       Cargo
                                              organizing     Agent
                                              Product
                                              Transport
   Transport Barter
 Sends evaluation result
          Notifiy Customer
             Proposals
   information is
        Agent for evaluating
   notified.                                matching
        the Barter Requests
                                               Transport
                                               Information




Customer
 Agent2
                                           22
                                           22


  Case Study : Electronic Barter Application
Goal Model of exchangeBarterProducts System
                     Goal
                                                       23



Plan Level Exception Handling Definition
                                           HTN Plan for
                                        evaluateBarterProp
                                          osal agent goal




   Plan Level
                             Exceptional Execution Flow
   Exception
   Definition      Exception Handling
 For HTN Tasks          Task for
                   UnavaibleDatabase
                       Exception
                                                          24


Agent Level Exception Handling
  Customer
   Agent1
                                    Barter
                                  Management
                                    Agent


  When anNotifiy Customer
  Customer agentBarter
             exception
          Agent for evaluating
               Proposals
              regular
  occurs the proposal
  cancels
          the Barter Requests
  execution flow is                            matching
  changed.
                                         The proposal
             Participant agents          of crashed
             are notified                agent is
                                         cancelled


  Customer
   Agent2
                                            25


Agent Level Exception Handling Goal Model




                   Exceptional agent
                    goal definition
                                       26


Multi-agent Level Exception Handling
                     inverseOf


        inverseOf definition
       between system goals
                                                     27



• Introduction

• Exception Handling Mechanism for Goal Oriented
  MASs

• Abstact Exception Handling Architecture for MASs

• Our Implementation

• Case Study : Electronic Barter Application

• Other Exception Handling Approaches

• Conclusion
                                           28




Other Exception Handling Approaches
• We categorize other exception handling
  approaches in two main category.

• Organizational View

• Agent View
                                                     29




Other Exception Handling Approaches
• Organizational View: These approaches
  bring some organizational entities to MAS and
  these entities monitor agents by listening their
  internal events and messages to detect
  exceptional situations.

  ▫ Centralized

  ▫ Decentralized
                                                        30



Other Exception Handling Approaches
• Centralized organizational view define an exception
  handling entity in the architecture of MAS for
  handling exceptions.

  ▫ Tripathi and Miller's guardian agent
  ▫ Klein and Dellarocas's Exception Handling
    Service(EHS).

• Decentralized organizational view spread
  responsibility of handling exceptions through more
  than one organizational entity.

  ▫ Haegg's sentinel agents.
                                                  31




Other Exception Handling Approaches

• Agent View: These approches listen messages
  and events of the agent, but they propose a
  mechanism to handle the exceptions inside the
  agent.

 ▫ SaGE framework.
                                                             32

   Comparison of Exception Handling
             Approaches
• Organizational views’ definitions are weak, they need so
  much information and resource (agents/services) for
  handling exceptions.

• Decentralized views need an agent for each agent.

• Organizational views do not consider agent internal
  knowledge.

• Organizational views do not support agent autonomy.

• Agent views focus on agent internal exceptions, do not
  consider organizational exceptions.
                                                     33



• Introduction

• Exception Handling Mechanism for Goal Oriented
  MASs

• Abstact Exception Handling Architecture for MASs

• Our Implementation

• Case Study : Electronic Barter Application

• Other Exception Handling Approaches

• Conclusion
                                                     34


                Conclusion
• We propose an exception handling approach for
  goal-oriented MASs.
• Our approach is classified in agent view but MAS
  Level Exception make it applicable in
  organizational view.
• And we propose life cycle that supports
  autonomy of agents.
• Its obeserved with the case study that our
  approach support the robustness and reliability
  of MASs.
                         35




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posted:10/6/2013
language:German
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