1. EEL 5937 The Bond Agent System (3) EEL 5937 Multi Agent Systems Lecture 17, March. 4, 2003 Lotzi Bölöni

2. EEL 5937 Review of the homework Generally, speaking, those who submitted, solved the problem. Let’s see a typical solution. Both the judge and the prisoner needs one active strategy. You might want to add extra states (e.g. for waiting, error handling etc.).

3. EEL 5937 Blueprint for the Judge createPlane("JudgePlane") import homework s = homework.JudgeStrategy(agent) addFirstState(s, "Judge") s = bond.strategydb.WaitAndTransitionStrategy(agent, 5000, SUCCESS) addState(s, "Wait") addTransition('Judge', 'Wait‘, SUCCESS) addTransition('Wait', 'Judge', SUCCESS)

4. EEL 5937 Blueprint for the prisoner Prisoner.py import homework createPlane(“PrisonerPlane") s = homework.PrisonerStrategy(agent, 0) addFirstState(s, "Prisoner") s = bond.strategydb.WaitAndTransitionStrategy(agent, 5000, SUCCESS) addState(s, "Wait") addTransition('Prisoner', 'Wait',SUCCESS) addTransition('Wait', 'Prisoner', SUCCESS)

5. EEL 5937 Judge strategy package homework; import bond.agent.BondAgent; import bond.agent.strategy.Strategy; import bond.util.fsm.FSM; import bond.util.fsm.FSMException; import jade.lang.acl.ACLMessage; import jade.lang.acl.MessageTemplate; import jade.core.AID; public class JudgeStrategy extends Strategy { private FSM judgeFSM; private String[] prisoners; // list of prisoners private String[] responses; // list of responses by prisoners private String[] judgement; //judgement for prisoners private final String QUESTION = "Do you confess for this crime?"; private final String CONFESS = "Confess"; private final String NOT_CONFESS = "Not Confess";

6. EEL 5937 Judge strategy public JudgeStrategy(BondAgent a) { super(a); String states[] = { "AskPrisoners", "GetResponseFromPrisoners", "makeJudgement", "sendVerdict", }; judgeFSM = new FSM("Judge",states); judgeFSM.addTransition("AskPrisoners", "GetResponseFromPrisoners"); judgeFSM.addTransition("GetResponseFromPrisoners", "makeJudgement"); judgeFSM.addTransition("makeJudgement","sendVerdict"); }

7. EEL 5937 Judge strategy public void action() { if (judgeFSM.stateIs("AskPrisoners")) { askPrisoners(); // Send questions to prisoners } if (judgeFSM.stateIs("GetResponseFromPrisoners")) { getResponseFromPrisoners(); // Wait for response from prisoners } if (judgeFSM.stateIs("makeJudgement")) { makeJudgement(); // Given the responses, make a judgement } if (judgeFSM.stateIs("sendVerdict")) { sendVerdict(); // Send verdict to respective prisoners }

8. EEL 5937 Judge strategy – asking the prisoners private void askPrisoners() throws FSMException { ACLMessage question = new ACLMessage(ACLMessage.REQUEST); question.setSender(theAgent.getAID()); question.addReceiver(new AID(prisoners[0],false)); question.addReceiver(new AID(prisoners[1],false)); question.setContent(QUESTION); theAgent.send(question); judgeFSM.setState("GetResponseFromPrisoners"); }

9. EEL 5937 Judge strategy – wait for responses private void getResponseFromPrisoners() throws FSMException { MessageTemplate mt = MessageTemplate.MatchPerformative(ACLMessage.AGREE); mt = MessageTemplate.or(MessageTemplate.MatchPerformative(ACLMessage.REFUSE), mt); ACLMessage response = theAgent.receive(mt); if (response == null) { block(500); return; } for (int i=0; i<prisoners.length; i++) { if (response.getSender().getLocalName().equalsIgnoreCase(prisoners[i])) { if (response.getPerformative() == ACLMessage.AGREE) { responses[i] = CONFESS; } else if (response.getPerformative() == ACLMessage.REFUSE) { responses[i] = NOT_CONFESS; } break; } // end if } // end for } // end if (mt == null)... else if (responses[0] != null && responses[1] != null) { judgeFSM.setState("makeJudgement"); } } // end getResponseFromPrisoners

10. EEL 5937 Judge strategy – making the judgement private void makeJudgement() throws FSMException { judgement = new String[2]; if (responses[0].equalsIgnoreCase(CONFESS) && responses[1].equalsIgnoreCase(CONFESS)) { judgement[0] = "You have been jailed for 2 years"; judgement[1] = "You have been jailed for 2 years"; } else if (responses[0].equalsIgnoreCase(NOT_CONFESS) && responses[1].equalsIgnoreCase(NOT_CONFESS)) { judgement[0] = "You have been jailed for 1 year"; judgement[1] = "You have been jailed for 1 year"; } else { if (responses[0].equalsIgnoreCase(CONFESS)) { judgement[0] = "You are free !!!"; judgement[1] = "You are jailed for 3 years. Bad Luck!!!"; } else { judgement[1] = "You are free !!!"; judgement[0] = "You are jailed for 3 years. Bad Luck!!!"; } judgeFSM.setState("sendVerdict"); }

11. EEL 5937 Judge strategy – sending the verdict private void sendVerdict() throws FSMException { for (int i=0; i<prisoners.length;i++) { ACLMessage inform = new ACLMessage(ACLMessage.INFORM); inform.setSender(theAgent.getAID()); inform.addReceiver(new AID(prisoners[i],false)); inform.setContent(judgement[i]); theAgent.send(inform); } judgeFSM.setState("ReceiveCase"); }

12. EEL 5937 Handling user interfaces There are two choices here (A) Integrate the GUI with the strategy. Create an external class with the user interface, inherit it from JFrame, and directly point to it from the strategy. –Advantage: simple, you have direct access –Disadvantage: difficult –Example: bond/applications/prisoners_dilemma/simple (B) Create a separate user interface, as a separate strategy. –Advantage: separation of UI and functionality. Agents can be assembled, modified. –Disadvantage: more complex interaction, through the agent state. –Example: bond/applications/prisoners_dilemma/separateui

13. EEL 5937 Bootstrapping a multi-agent system

14. EEL 5937 Bootstrapping multi-agent systems Creating a set of agents which will act in a coalition. –In practical deployments, only agents working on behalf a single user are started like this. All the projects can be seen as examples of this. –Even if some of the agents in the projects are in adversarial relations. It can be done: –By hand using the Jade Remote Agent Manager. –By a bootstrapping agent.

15. EEL 5937 Bootstrapping agent. A bootstrap agent –Bootstrap.py (see example in the prisoners dilemma directory) –Takes a bootstrap file as input. –Starts the agents described (potentially on multiple machines) –Terminates. The format of the bootstrap file: Example bootstrap file: localhost bond\applications\prisoners_dilemma\simple\Judge.py Judge localhost bond\applications\prisoners_dilemma\simple\Prisoner1.py Prisoner1 localhost bond\applications\prisoners_dilemma\simple\Prisoner1.py Prisoner2

16. EEL 5937 Basic strategies. Strategy database

17. EEL 5937 Strategy Database Contains a collection of general purpose strategies. Promotes code reuse. Utility strategies –Running applications System strategies –Running applications, running scripts –Transfering files (FTP etc) –Mail, Http Agent manipulation –Remotely starting, stopping agents, etc. Agent protocol implementation –Question/Reply –Contract net, auctions, etc.

18. EEL 5937 Utility strategies: WaitAndTransitionStrategy Usage: –addState(WaitAndTransitionStrategy()) –addState(WaitAndTransitionStrategy(5000, SUCCESS)) Functionality: –Waits for the specified number of milliseconds than performs the transition specified. Transition: –The transition specified (SUCCESS by default)

19. EEL 5937 Utility strategies: DummyStrategy Usage: –addState(DummyStrategy()) Functionality: –Blocks indefinitely. (Used for debugging) Transition: –None.

20. EEL 5937 Utility strategies: ShowMessageStrategy, ShowErrorStrategy Usage: –addState(ShowMessageStrategy(“Message”)) –addState(ShowMessageStrategy(“ErrorMessage”)) Functionality: –Shows a message / error message in a dialog box. Transitions when the user clicks on the button. Transition: –SUCCESS

21. EEL 5937 Utility strategies: ChoiceStrategy Usage: –addState(ChoiceStrategy(“Proceed?”)) Functionality: –Shows a dialog with the message with two buttons. Transition: –SUCCESS if the Yes button is pressed. –FAILURE if the No button is pressed.

22. EEL 5937 Utility strategies: ExitAgentStrategy Usage: –addState(ExitAgentStrategy()) Functionality: –Terminates the agent by calling doDelete(). Transition: –None (the agent will be terminated).