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

A Policy-based Infrastructure for the Dynamic Control of Agent Mobility Gianluca Tonti , Rebecca Montanari {gtonti, rmontanari}@deis.unibo.it D.E.I.S. Department University of Bologna - Italy POLICY2002 Monterey 6/10/2002

Outline � Motivations � A policy-controlled Mobile Agent Framework: POEMA � Conclusions 2 POLICY2002 Monterey 6/10/2002

Motivations Mobility adds complexity to the design and development of applications Programmers have to explicitly deal with the allocation of agents 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? …Solution � Separation of concerns: mobility and application logic 3 POLICY2002 Monterey 6/10/2002

Policy-based approach to Control Mobility IDEA Policies for governing the mobility behaviour of Mobile Agents Mobility policies specify: when, where and which unit of mobility must migrate Advantages of policy-controlled mobility � Clean separation between mobility concerns and the application logic Possibility to facilitate dynamic reconfiguration of mobility strategies � Possibility to specify mobility behaviour at a higher level of abstraction 4 POLICY2002 Monterey 6/10/2002

Case Study UserInterface Explorer UserInterface Agent Agent Agent Emergency Server Client Stub Client Stub PDA Computing Equipment Ambulance Hospital networks Ambulances set Explorer Agent 5 POLICY2002 Monterey 6/10/2002

Mobility Policies Event-triggered declarative policies for controlled mobility Obligation Ponder Policies Examples inst oblig MobPol1 { inst oblig MobPol2 { on Login(User, PDA); on PDA_Battery_Low(); subject s = subject s = agents/UserInterfaceAgent; agents/UserInterfaceAgent; do s.go(Ambulance12, “run”); do s.go(PDA, “run”); when when MonitoringSystem.isReachable(Ambulance12); } MonitoringSystem.isReachable(PDA); } Facilities for lifecycle management 6 POLICY2002 Monterey 6/10/2002

POEMA Policy- -Based Architecture Based Architecture POEMA Policy Applications Mobile Agent Mobile Agent POEMA Code Data Policies Code Data Policies Computational Environment Upper-layer Policy Middleware Services Policy Policy Policy Repository Specification Enforcement Coordinator Service Service Service Service Lower-layer Services Monitoring Event Service Service CE Services …...…... Naming Migration Communication Basic Operating System 7 Host POLICY2002 Monterey 6/10/2002

Policy Enforcement Service Policy Enforcement is composed of a set of specialized tasks: POEMA System Interface POEMA Policy Enforcer 1 3 2 Policy Policy Constraint Loader Interpreter Verifier 8 POLICY2002 Monterey 6/10/2002

Policy-controlled Mobile Agents (1.) If an agent is the policy subject, it has to actively enforce the policy Agent Policy Worker Worker Event start Listener POEMA AGENT Agent Policy Ev. x Ev. y CODE ENGINE Agent Agent Policies Data Possibility of conflicts Computational between agent code and Mobility Policy part Policy Execution part 9 POLICY2002 Monterey 6/10/2002

Policy Controlled Mobile Agents (2.) class UserInterfaceAgent extends PolicyControlledAgent … void run() { startPersonalInfoInterface (); request_for_ confirmation(); criticalSection(“savePersonalData”); startSymptomaticDataInterface(); … } UserInterfaceAgent … MobPol1 MobPol2 System Interface POEMA Policy Policy Enforcement Infrastructure Repository Service 10 POLICY2002 Monterey 6/10/2002

Conclusions Policy-based approach to control mobility can simplify application design and maintenance Dynamic modification of agent mobility behaviour via changes in policy specifications 11 POLICY2002 Monterey 6/10/2002