Developing Intelligent Agent Systems A Practical Guide

Contents
Foreword from the Series Editor ix
Preface xi
Acknowledgement xiii
1 Agents and Multi-Agent Systems 1
1.1 What is an Intelligent Agent? . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Why are Agents Useful? . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Concepts for Building Agents 7
2.1 Situated Agents: Actions and Percepts . . . . . . . . . . . . . . . . . . . 7
2.2 Proactive and Reactive Agents: Goals and Events . . . . . . . . . . . . 8
2.3 Challenging Agent Environments: Plans and Beliefs . . . . . . . . . . . 10
2.4 Social Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5 Agent Execution Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.5.1 Choice of Plan to Execute . . . . . . . . . . . . . . . . . . . . . 14
2.5.2 Many Ways to Achieve a Goal . . . . . . . . . . . . . . . . . . 16
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 Overview of the Prometheus Methodology 21
3.1 Why a New Methodology? . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2 Prometheus: A Brief Overview . . . . . . . . . . . . . . . . . . . . . . 23
3.2.1 System Specification . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.2 Architectural Design . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.3 Detailed Design . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3 Guidelines for Using Prometheus . . . . . . . . . . . . . . . . . . . . . 27
3.4 Agent-Oriented Methodologies . . . . . . . . . . . . . . . . . . . . . . . 29
4 System Specification 33
4.1 Goal Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.1.1 Identify Initial Goals . . . . . . . . . . . . . . . . . . . . . . . . 35
4.1.2 Goal Refinement . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.2 Functionalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.3 Scenario Development . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.3.1 Goal Step Details . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.3.2 Capturing Alternative Scenarios . . . . . . . . . . . . . . . . . . 46
4.4 Interface Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.4.1 Percepts and Actions . . . . . . . . . . . . . . . . . . . . . . . . 48
4.4.2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.5 Checking for Completeness and Consistency . . . . . . . . . . . . . . . 51
5 Architectural Design: Specifying the Agent Types 53
5.1 Deciding on the Agent Types . . . . . . . . . . . . . . . . . . . . . . . 56
5.2 Grouping Functionalities . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.3 Review Agent Coupling – Acquaintance Diagrams . . . . . . . . . . . . 63
5.4 Develop Agent Descriptors . . . . . . . . . . . . . . . . . . . . . . . . . 65
6 Architectural Design: Specifying the Interactions 67
6.1 Interaction Diagrams from Scenarios . . . . . . . . . . . . . . . . . . . 68
6.2 Interaction Protocols from Interaction Diagrams . . . . . . . . . . . . . 74
6.3 Develop Protocol and Message Descriptors . . . . . . . . . . . . . . . . 77
7 Finalizing the Architectural Design 81
7.1 Overall System Structure . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.2 Identifying Boundaries of the Agent System . . . . . . . . . . . . . . . 82
7.3 Describing Percepts and Actions . . . . . . . . . . . . . . . . . . . . . . 84
7.4 Defining Shared Data Objects . . . . . . . . . . . . . . . . . . . . . . . 88
7.5 System Overview Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.6 Checking for Completeness and Consistency . . . . . . . . . . . . . . . 94
7.6.1 Consistency between Agents and Functionalities . . . . . . . . . 95
7.6.2 Consistency between Interaction Diagrams, Scenarios
and Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
7.6.3 Consistency of Communication Specifications . . . . . . . . . . 96
7.6.4 Consistency between Descriptors and the System
Overview Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 97
8 Detailed Design: Agents, Capabilities and Processes 99
8.1 Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
8.2 Agent Overview Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . 102
8.3 Process Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
8.4 Develop Capability and Process Descriptors . . . . . . . . . . . . . . . 106
9 Detailed Design: Capabilities, Plans and Events 109
9.1 Capability Overview Diagrams . . . . . . . . . . . . . . . . . . . . . . . 110
9.2 Sub-tasks and Alternative Plans . . . . . . . . . . . . . . . . . . . . . . 112
9.2.1 Identifying Context Conditions . . . . . . . . . . . . . . . . . . 113
9.2.2 Coverage and Overlap . . . . . . . . . . . . . . . . . . . . . . . 115
9.3 Events and Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
9.4 Action and Percept Detailed Design . . . . . . . . . . . . . . . . . . . . 117
9.5 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
9.6 Develop and Refine Descriptors . . . . . . . . . . . . . . . . . . . . . . 118
9.7 Checking for Completeness and Consistency . . . . . . . . . . . . . . . 119
9.7.1 Agent Completeness . . . . . . . . . . . . . . . . . . . . . . . . 120
9.7.2 Missing or Redundant Items . . . . . . . . . . . . . . . . . . . . 120
9.7.3 Consistency between Artifacts . . . . . . . . . . . . . . . . . . . 121
9.7.4 Impotant Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 123
10 Implementing Agent Systems 125
10.1 Agent Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
10.2 JACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
10.3 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
10.3.1 Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
10.3.2 Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
10.3.3 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
10.3.4 Messages/Events . . . . . . . . . . . . . . . . . . . . . . . . . . 134
10.3.5 Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
10.4 Automatic Generation of Skeleton Code . . . . . . . . . . . . . . . . . . 138
A Electronic Bookstore 139
B Descriptor Forms 199
C The AUML Notation 205
Bibliography 215
Index 221

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