Message Passing

Content = String

Content = Bean

Commands-As-Objects: Math Command

public class MathCommand implements java.io.Serializable {
private String operation; // +, *, -, /, %, <, etc.
private float arg1;
private float arg2;
public void setOperation(String op) { operation = op; }
public String getOperation() { return operation; }
public float getArg1() { return arg1; }
public void setArg1(float arg) { arg1 = arg; }
public float getArg2() { return arg2; }
public void setArg2(float arg) { arg2 = arg; }
}

Math Client

public class MathClient extends Agent {
protected void setup() {
MathCommand cmmd = new MathCommand();
cmmd.setOperation("*");
cmmd.setArg1(6);
cmmd.setArg2(7);
ACLMessage msg = new ACLMessage( ACLMessage.REQUEST );
msg.addReceiver(new AID( "dt", AID.ISLOCALNAME));
try {
msg.setContentObject(cmmd);
}
catch (Exception e) {
System.err.println(e.getMessage());
}
send(msg);
ACLMessage result = blockingReceive();
System.out.println("result = " + result.getContent());
}
}

Math Server

A math server just adds a math behavior:

public class MathServer extends Agent {
protected void setup() {
addBehaviour(new MathBehavior(this));
}
}

Here's the server's behavior:

class MathBehavior extends CyclicBehaviour {
public MathBehavior(Agent a) { super(a); }

protected String execute(MathCommand cmmd) {
String op = cmmd.getOperation();
float arg1 = cmmd.getArg1();
float arg2 = cmmd.getArg2();
if (op.equals("+")) return "" + (arg1 + arg2);
if (op.equals("*")) return "" + (arg1 * arg2);
if (op.equals("-")) return "" + (arg1 - arg2);
if (op.equals("/")) return "" + (arg1 / arg2);
if (op.equals("%")) return "" + (arg1 % arg2);
if (op.equals("<")) return "" + (arg1 < arg2);
if (op.equals("=")) return "" + (arg1 = arg2);
return "unknown operator: " + op;
}

public void action() {
ACLMessage msg = myAgent.receive();
if (msg == null) { block(); return; } // cool!
try {
MathCommand cmmd = (MathCommand)msg.getContentObject();
String result = execute(cmmd);
ACLMessage answer = msg.createReply();
answer.setContent(result);
myAgent.send(answer);
} catch(Exception e) {
System.err.println(e.getMessage());
}
}
}

Content = ???

Useful Constants

public interface MathVocabulary {
public static final String MATH_COMMAND = "MathCommand";
public static final String MATH_COMMAND_ARG1 = "arg1";
public static final String MATH_COMMAND_ARG2 = "arg2";
public static final String MATH_COMMAND_OP = "operation";
}

The Math Ontology

public class MathOntology extends Ontology {
public static final String ONTOLOGY_NAME = "Math-Ontology";
// MathOntology is a singleton:
private static MathOntology instance = new MathOntology();
public static MathOntology getInstance() { return instance; }
private MathOntology() {
super(ONTOLOGY_NAME, BasicOntology.getInstance());
try {

AgentActionSchema as =
new AgentActionSchema(MathVocabulary.MATH_COMMAND);
add(as, MathCommand.class);
as.add(MathVocabulary.MATH_COMMAND_ARG1,
(PrimitiveSchema) getSchema(BasicOntology.FLOAT),
ObjectSchema.MANDATORY);
as.add(MathVocabulary.MATH_COMMAND_ARG2,
(PrimitiveSchema) getSchema(BasicOntology.FLOAT),
ObjectSchema.MANDATORY);
as.add(MathVocabulary.MATH_COMMAND_OP,
(PrimitiveSchema) getSchema(BasicOntology.STRING),
ObjectSchema.MANDATORY);
} catch(Exception e) {
System.err.println(e.getMessage());
}
}
}

The Math Client

public class MathClient extends Agent {
private Codec codec = new SLCodec(); // ???
private Ontology ontology = MathOntology.getInstance();

protected void setup() {

// Register language and ontology
getContentManager().registerLanguage(codec);
getContentManager().registerOntology(ontology);

MathCommand cmmd = new MathCommand();
cmmd.setOperation("*");
cmmd.setArg1(6);
cmmd.setArg2(7);
sendMessage(
ACLMessage.REQUEST, cmmd, new AID( "dt", AID.ISLOCALNAME));

ACLMessage result = blockingReceive();
System.out.println("result = " + result.getContent());
}

void sendMessage(
int performative, AgentAction action, AID server) {
ACLMessage msg = new ACLMessage(performative);
msg.setLanguage(codec.getName());
msg.setOntology(ontology.getName());
try {
getContentManager().fillContent(
msg, new Action(server, action));
msg.addReceiver(server);
send(msg);
} catch (Exception e) {
System.err.println(e.getMessage());
}
}
}

The Math Server

public class MathServer extends Agent {
private Codec codec = new SLCodec();
private Ontology ontology = MathOntology.getInstance();
protected void setup() {
// Register language and ontology
getContentManager().registerLanguage(codec);
getContentManager().registerOntology(ontology);

addBehaviour(new MathBehavior(this));
}
}

Server behavior

class MathBehavior extends CyclicBehaviour {
// etc.
public void action() {
ACLMessage msg = myAgent.receive();
if (msg == null) { block(); return; } // cool!
try {
ContentElement content =
myAgent.getContentManager().extractContent(msg);
Concept action = ((Action)content).getAction();
MathCommand cmmd = (MathCommand)action;

String result = execute(cmmd);
ACLMessage answer = msg.createReply();
answer.setContent(result);
myAgent.send(answer);
} catch(Exception e) {
System.err.println(e.getMessage());
}
}
}