A Policy-based Infrastructure for the Dynamic Control of Agent - - PowerPoint PPT Presentation

POLICY2002 Monterey 6/10/2002

A Policy-based Infrastructure for the Dynamic Control

• f Agent Mobility

Gianluca Tonti, Rebecca Montanari {gtonti, rmontanari}@deis.unibo.it D.E.I.S. Department University of Bologna - Italy

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Outline

A policy-controlled Mobile Agent Framework: POEMA Motivations Conclusions

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Programmers have to explicitly deal with the allocation of agents

Motivations

Mobility adds complexity to the design and development of applications Mobility specifications embedded into the agent code are not adequate to cope with the frequent changes of the environment state need of flexibility need of flexibility

Question… HOW

HOW to allow dynamic changes in the mobility behaviour of agents without reengineering the agent code? Separation of concerns: mobility and application logic

…Solution

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Policy-based approach to Control Mobility

IDEA Policies for governing the mobility behaviour of Mobile Agents Possibility to specify mobility behaviour at a higher level of abstraction Clean separation between mobility concerns and the application logic Advantages of policy-controlled mobility Possibility to facilitate dynamic reconfiguration of mobility strategies

when, where and which unit of mobility must migrate Mobility policies specify:

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Case Study

Computing Equipment

Ambulance Hospital networks

PDA

Explorer Agent UserInterface Agent

Emergency Server Client Stub Client Stub

UserInterface Agent

Ambulances set

Explorer Agent

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Mobility Policies

Event-triggered declarative policies for controlled mobility Facilities for lifecycle management Obligation Ponder Policies inst oblig MobPol2 {

• n PDA_Battery_Low();

subject s = agents/UserInterfaceAgent; do s.go(Ambulance12, “run”); when

MonitoringSystem.isReachable(Ambulance12);

} inst oblig MobPol1 {

• n Login(User, PDA);

subject s = agents/UserInterfaceAgent; do s.go(PDA, “run”); when

MonitoringSystem.isReachable(PDA);

} Examples

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Host Operating System Computational Environment

Basic CE Services Lower-layer Services Upper-layer Services

Naming Migration

…...…...

Communication Event Service Monitoring Service Policy Specification Service Policy Enforcement Service Repository Service Policy Coordinator Service Policy Middleware

POEMA Policy POEMA Policy-

• Based Architecture

Based Architecture

POEMA Applications

Policies

Mobile Agent

Code Data Policies

Mobile Agent

Code Data

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Policy Enforcement Service

Policy Interpreter Policy Loader Constraint Verifier Policy Enforcer 1 2 3

POEMA System Interface

POEMA

Policy Enforcement is composed of a set of specialized tasks:

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Policy-controlled Mobile Agents (1.)

POEMA AGENT Agent Policies Agent Data

Agent Worker Policy Worker Policy ENGINE Agent CODE

Ev.x Ev.y

Event Listener

start

Mobility Policy part Computational part If an agent is the policy subject, it has to actively enforce the policy

Possibility of conflicts between agent code and Policy Execution

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Policy Controlled Mobile Agents (2.)

Policy Enforcement Service

class UserInterfaceAgent extends PolicyControlledAgent … void run() { startPersonalInfoInterface (); request_for_ confirmation(); criticalSection(“savePersonalData”); startSymptomaticDataInterface(); … } …

System Interface

POEMA Infrastructure

Policy Repository MobPol2 MobPol1 UserInterfaceAgent

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Conclusions

Dynamic modification of agent mobility behaviour via changes in policy specifications Policy-based approach to control mobility can simplify application design and maintenance