EEL 5937

The Bond Agent System(3)

EEL 5937 Multi Agent Systems

Lecture 17, March. 4, 2003

Lotzi Bölöni

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.).

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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)

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)

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Judge strategypackage 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";

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Judge strategypublic 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");

}

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Judge strategypublic 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

}

}

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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");

}

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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

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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"); }

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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");

}

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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

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Bootstrapping a multi-agent system

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.

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:<host> <blueprint file> <agent name>

• 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

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Basic strategies.Strategy database

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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.

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Utility strategies: WaitAndTransitionStrateg

y• 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)

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Utility strategies: DummyStrategy

• Usage:– addState(DummyStrategy())

• Functionality:– Blocks indefinitely. (Used for debugging)

• Transition:– None.

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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

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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.

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Utility strategies: ExitAgentStrategy

• Usage:– addState(ExitAgentStrategy())

• Functionality:– Terminates the agent by calling doDelete().

• Transition:– None (the agent will be terminated).