1 KIMAS 2003Dr. K. Kleinmann An Infrastructure for Adaptive Control of Multi-Agent Systems Dr. Karl Kleinmann, Richard Lazarus, Ray Tomlinson KIMAS, October 1, 2003

2 KIMAS 2003Dr. K. Kleinmann Control of DMAS: Problem Description Characteristics of Distributed Multi-Agent Systems (DMAS) reason that formal methods of control theory are rarely applied in software engineering for agent systems “What makes DMAS a hard (complex) control problem?” –Dynamic system boundaries, interactions and communication paths –System size, number of internal states, degrees of freedom (flexibility) –Strong couplings between system states (shared resources) “What makes DMAS a unique control problem?” –Shape of cost functions and performance criteria Changes of control inputs at (almost) no cost (nonlinear impact) –Explicit model available, accurate description of behavior (code) System as its own simulator –Extensive experimentation “for free” (automated testing) Control approaches and parameter variations by “trial and error”

3 KIMAS 2003Dr. K. Kleinmann Cougaar Project Background and Control Objectives Paper presents the Control Infrastructure of the Cougaar Distributed Agent System Cougaar is an Open Source Agent Infrastructure developed under the DARPA Programs –ALP ( ): Military Logistics Planning –UltraLog ( ): Survivable Logistics Planning and Execution Primary System Function –Logistics Plan Robustness Function –Maintain Processing Infrastructure despite Loss of Resources Security Function –Maintain System Integrity despite Information Attacks Military Logistics Operation UltraLog DMAS Logistics Requirements Logistic Actions (Plan) SW Failures HW Failures

4 KIMAS 2003Dr. K. Kleinmann Cougaar Architecture Overview 100% Java Architecture for building large DMAS Proven Scalability –Prototype with 500 distinct agents distributed over 5LAN network of >100 machines Two-Level interaction model –Intra-agent blackboard for tightly- coupled interactions –Inter-agent message passing for scalable loosely-coupled interactions Distributed object management –Prototype/delegation data model –Capabilities-based representations Two-Dimensional containment model –Components can be both containers and plugins TRANSCOM 1BDE 2BDE

5 KIMAS 2003Dr. K. Kleinmann Control Levels designed to achieve Control Objectives Agent Infrastructure-Level Control –Parameters of Components within an Agent –“Local Agent Autonomy” (e.g., Message Compression; Status Report Rate) Military Logistics Operation UltraLog DMAS Logistics Requirements Logistic Actions (Plan) SW Failures HW Failures Agent Components Agent Controller TRANSCOM 1BDE 2BDE UltraLog DMAS Application-Level Control –Complex Actions or Sequences of Actions composed of Control Primitives –“Specific Defenses against Stresses” (e.g., Load Balancing; Agent Restart)

6 KIMAS 2003Dr. K. Kleinmann The Cougaar Control Infrastructure

7 KIMAS 2003Dr. K. Kleinmann Example (Part of the Open Source Code Base) 2 Agents –(Consumer); Provider 2 Sensor Inputs (Conditions) –Task Rate; Avail. CPU 1 Control Input (Operating Mode) –Task Allocator Plugin Mode (Tradeoff Accuracy vs Speed) Task Allocator Plugin Adaptivity Engine Task Rate CPU Allocation Alg. Provider Agent Consumer Agent

8 KIMAS 2003Dr. K. Kleinmann Interpretation of the Approach Infrastructure allows both feedforward and feedback control, depending on selection of Conditions and Operating Modes Heuristic parametrization of Plays makes Adaptivity Engine typically nonlinear controller (-> fuzzy control) If Plays in Adaptivity Engine are modified according to TechSpecs or constrained by Policies, Control System becomes truly “Adaptive” Rule Matrix in Example:

9 KIMAS 2003Dr. K. Kleinmann Conclusions Presented Agent-level Control Infrastructure for the Open Source Cougaar Architecture –Generic Approach allows to address Control Objectives of a DMAS Survivability Application –Connects Software Engineering with Control Theory Models in Order to leverage Control Theory Methodologies Future Research Issues –Components publishing TechSpecs –Deconfliction of Application-level Control Strategies

10 KIMAS 2003Dr. K. Kleinmann For more information … BBN Technologies: Cougaar: UltraLog: Other Cougaar-related KIMAS’03 papers: –“Multi-Tier Communication Abstractions for Distributed Multi-Agent Systems”, M. Thome, et al –“Multi-resolutional Knowledge Representation for Logistics Systems using Prototypes,Properties and Behaviors”, J. Berliner, et al