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TELECOM ITALIA GROUP

JADE14 September 2010

Giovanni CaireGiovanni CaireGiovanni CaireGiovanni Caire

Giovanni.caire@telecomitalia.it

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Agenda

Overview

Creating Agents

Agent tasks

Agent communication

The yellow pages service

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JADE

INFOR

M

REQUEST PROP

OSE

AGREE

REFUSE

A middleware for applications based on the agent paradigmA middleware for applications based on the agent paradigmA middleware for applications based on the agent paradigmA middleware for applications based on the agent paradigm

ProvidesProvidesProvidesProvides

The AgentAgentAgentAgent and BehaviourBehaviourBehaviourBehaviour (a task that an agent can execute) abstractions

Transparent distributiondistributiondistributiondistribution of components (agents)

PeerPeerPeerPeer----totototo----peerpeerpeerpeer communicationcommunicationcommunicationcommunication based on asynchronous message passing

Publish-subscribe

discoverydiscoverydiscoverydiscovery mechanisms Fully written inFully written inFully written inFully written in JavaJavaJavaJava

Open SourceOpen SourceOpen SourceOpen Source

http://jade.tilab.com

~230.000 downloads

Current version: 4.014.014.014.01

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Architecture

JADE

Container

Container

Main

ContainerPLATFORM

AMS DF

PLATFORM 2JADE

AMS DF

Main

Container

JADE JADE

host1

host2 host3

host4

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The communication model

A1 A2

Prepare themessage to A2

Get themessage fromthe messagequeue andprocess it

JADE distributed runtime

(PROPOSE(PROPOSE(PROPOSE(PROPOSE

:sender A1:sender A1:sender A1:sender A1

:receiver A2:receiver A2:receiver A2:receiver A2

:content:content:content:content Cinema eveningCinema eveningCinema eveningCinema evening

:language:language:language:language EnglishEnglishEnglishEnglish

:ontology:ontology:ontology:ontology CinemaCinemaCinemaCinema----ontologyontologyontologyontology

))))

Based onBased onBased onBased on asynchronousasynchronousasynchronousasynchronous message passingmessage passingmessage passingmessage passing

Message format defined by theMessage format defined by theMessage format defined by theMessage format defined by the ACLACLACLACL language (FIPA)language (FIPA)language (FIPA)language (FIPA)

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Agenda

Overview

Creating Agents

Agent tasks

Agent communication

The yellow pages service

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The HelloWorld agent

import jade.core.Agent;

public class HelloWorldAgent extends Agent {

protected void setup() {

System.out.println(Hello World! my name is +getAID().getName());

}

}

AAAA type of agenttype of agenttype of agenttype of agent is created by extending theis created by extending theis created by extending theis created by extending the jade.core.Agent classclassclassclass

and redefining theand redefining theand redefining theand redefining the setup() method.method.method.method.

EachEachEachEach Agent instanceAgent instanceAgent instanceAgent instance is identified by anis identified by anis identified by anis identified by an AIDAIDAIDAID ((((jade.core.AID).).).).

An AID is composed of a unique name plus some addresses

An agent can retrieve its AID through the getAID() method of the Agent

class

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Local names, GUID and addresses

Agent names have the formAgent names have the formAgent names have the formAgent names have the form

The complete name of an agent must beThe complete name of an agent must beThe complete name of an agent must beThe complete name of an agent must be globally uniqueglobally uniqueglobally uniqueglobally unique....

TheTheTheThe defaultdefaultdefaultdefault platform name is /JADE

The platform name can be set using theThe platform name can be set using theThe platform name can be set using theThe platform name can be set using the name optionoptionoptionoption

Within a single JADE platform agents are referred through theirWithin a single JADE platform agents are referred through theirWithin a single JADE platform agents are referred through theirWithin a single JADE platform agents are referred through their namesnamesnamesnames

only.only.only.only.

Given the name of an agent its AID can be created asGiven the name of an agent its AID can be created asGiven the name of an agent its AID can be created asGiven the name of an agent its AID can be created as

AID id = new AID(localname, AID.ISLOCALNAME);

AID id = new AID(name, AID.ISGUID);

The addresses included in an AID are those of the platform (The addresses included in an AID are those of the platform (The addresses included in an AID are those of the platform (The addresses included in an AID are those of the platform (MTPsMTPsMTPsMTPs) and) and) and) andareareareare ONLYONLYONLYONLY used in communication between agents living onused in communication between agents living onused in communication between agents living onused in communication between agents living on differentdifferentdifferentdifferent

FIPA platformsFIPA platformsFIPA platformsFIPA platforms

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Main startup options summary

Switch optionsSwitch optionsSwitch optionsSwitch options

-gui (activate the management GUI)

-container (launch a peripheral container instead of a main container) KeyKeyKeyKey----value pair optionsvalue pair optionsvalue pair optionsvalue pair options

-host (the host where the Main Container is running)

-port (the port where the Main Container is running)

-detect-main ((find the Main Container automatically)-local-port (the port to be used by the starting container)

-agents (the agents to be started at bootstrap)

-conf (get startup options from a property file)

Command line examplesCommand line examplesCommand line examplesCommand line examplesjava cp ... jade.Boot gui agents john:hello.HelloWorldAgent

java cp ... jade.Boot container host avalon.telecomitalia.it

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Passing arguments to an agent

protected void setup() {System.out.println(Hallo World! my name is +getAID().getName());

Object[] args = getArguments();

if (args != null) {

System.out.println(My arguments are:);

for (int i = 0; i < args.length; ++i) {

System.out.println(- +args[i]);

}

}

}

It is possible to pass arguments to an agentIt is possible to pass arguments to an agentIt is possible to pass arguments to an agentIt is possible to pass arguments to an agent

java jade.Boot .... a:myPackage.MyAgent(arg1,arg2)

The agent can retrieve its arguments through the getArguments()

method of the Agent class

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Agent termination

protected void setup() {

System.out.println(Hallo World! my name is +getAID().getName());

Object[] args = getArguments();

if (args != null) {

System.out.println(My arguments are:);for (int i = 0; i < args.length; ++i) {

System.out.println(- +args[i]);

}

}

doDelete();

}

protected void takeDown() {

System.out.println(Bye...);

}

An agent terminates when itsAn agent terminates when itsAn agent terminates when itsAn agent terminates when its doDelete() method is called.() method is called.() method is called.() method is called.

On termination the agentOn termination the agentOn termination the agentOn termination the agentssss takeDown() method is invoked (intended to() method is invoked (intended to() method is invoked (intended to() method is invoked (intended to

include cleaninclude cleaninclude cleaninclude clean----up operations).up operations).up operations).up operations).

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Agenda

Overview

Creating Agents

Agent tasks

Agent communication

The yellow pages service

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The Behaviour class

The actual job that an agent does is typically carried out withiThe actual job that an agent does is typically carried out withiThe actual job that an agent does is typically carried out withiThe actual job that an agent does is typically carried out withinnnn

behavioursbehavioursbehavioursbehaviours

BehavioursBehavioursBehavioursBehaviours are created by extending theare created by extending theare created by extending theare created by extending thejade.core.behaviours.Behaviour classclassclassclass

To make an agent execute a task it is sufficient to create an inTo make an agent execute a task it is sufficient to create an inTo make an agent execute a task it is sufficient to create an inTo make an agent execute a task it is sufficient to create an instance ofstance ofstance ofstance of

the correspondingthe correspondingthe correspondingthe corresponding Behaviour subclass and call thesubclass and call thesubclass and call thesubclass and call the

addBehaviour() method of themethod of themethod of themethod of theAgent class.class.class.class.

EachEachEachEach BehaviourBehaviourBehaviourBehaviour subclass must implementsubclass must implementsubclass must implementsubclass must implement

public void action(): what the behaviour actually does

public boolean done(): whether the behaviour is finished

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Behaviour scheduling and execution

Behaviour switch occurs only when

the action() method of the currentlyscheduled behaviour returns.

An agent can execute severalAn agent can execute severalAn agent can execute severalAn agent can execute several behavioursbehavioursbehavioursbehaviours in parallel, however,in parallel, however,in parallel, however,in parallel, however, behaviourbehaviourbehaviourbehaviour

scheduling is not preemptive, butscheduling is not preemptive, butscheduling is not preemptive, butscheduling is not preemptive, but cooperativecooperativecooperativecooperative and everything occursand everything occursand everything occursand everything occurs

within awithin awithin awithin a single Java Threadsingle Java Threadsingle Java Threadsingle Java Thread

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setup()

Agent has been killed

(doDelete() method

called)?

Get the next behaviour from

the pool of active behaviours

b.action()

b.done()?

Remove currentBehaviour from

the pool of active behaviours

takeDown()

- Initializations

- Addition of initialbehaviours

- Agent life (execution

of behaviours)

- Clean-up operations

YES

YES

NO

NO

Highlighted in red

the methods thatprogrammers have

to/can implement

The agent executionmodel

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Behaviour types

One shotOne shotOne shotOne shot behavioursbehavioursbehavioursbehaviours....

Complete immediately and their action() method is executed only once.

Their done() method simply returns true.

jade.core.behaviours.OneShotBehaviour class

CyclicCyclicCyclicCyclic behavioursbehavioursbehavioursbehaviours....

Never complete and their action() method executes the same operation

each time it is invoked

Their done() method simply returns false.

jade.core.behaviours.CyclicBehaviour class

ComplexComplexComplexComplex behavioursbehavioursbehavioursbehaviours....

Embed a state and execute in their action() method different operations

depending on their state.

Complete when a given condition is met.

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Scheduling operations at given points in time

JADE provides two readyJADE provides two readyJADE provides two readyJADE provides two ready----made classes by means of which it is possiblemade classes by means of which it is possiblemade classes by means of which it is possiblemade classes by means of which it is possible

to easily implement behaviours that execute operations at givento easily implement behaviours that execute operations at givento easily implement behaviours that execute operations at givento easily implement behaviours that execute operations at given pointspointspointspoints

in timein timein timein timeWakerBehaviour

The action() and done() method are already implemented so that the

onWake() method (to be implemented by subclasses) is executed after a

given timeout

After that execution the behaviour completes.

TickerBehaviour

The action() and done() method are already implemented so that the

onTick() (to be implemented by subclasses) method is executed

periodically with a given period

The behaviour runs forever unless its stop() method is called.

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Agenda

Overview

Creating Agents

Agent tasks

Agent communication

The yellow pages service

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The communication model

A1 A2

Prepare themessage to A2

Get themessage fromthe messagequeue andprocess it

JADE distributed runtime

(PROPOSE(PROPOSE(PROPOSE(PROPOSE

:sender A1:sender A1:sender A1:sender A1

:receiver A2:receiver A2:receiver A2:receiver A2

:content:content:content:content Cinema eveningCinema eveningCinema eveningCinema evening

:language:language:language:language EnglishEnglishEnglishEnglish

:ontology:ontology:ontology:ontology CinemaCinemaCinemaCinema----ontologyontologyontologyontology

))))

Based onBased onBased onBased on asynchronousasynchronousasynchronousasynchronous message passingmessage passingmessage passingmessage passing

Message format defined by theMessage format defined by theMessage format defined by theMessage format defined by the ACLACLACLACL language (FIPA)language (FIPA)language (FIPA)language (FIPA)

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The ACLMessage class

Messages exchanged by agents are instances of theMessages exchanged by agents are instances of theMessages exchanged by agents are instances of theMessages exchanged by agents are instances of the

jade.lang.acl.ACLMessage class.class.class.class.

ProvideProvideProvideProvide accessoraccessoraccessoraccessor methods to get and set all the fields defined by themethods to get and set all the fields defined by themethods to get and set all the fields defined by themethods to get and set all the fields defined by theACL languageACL languageACL languageACL language

get/setPerformative();

get/setSender();

add/getAllReceiver();

get/setLanguage();

get/setOntology();

get/setContent();

....

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Sending and receiving messages

ACLMessage msg = new ACLMessage(ACLMessage.INFORM);

msg.addReceiver(new AID(Peter, AID.ISLOCALNAME));

msg.setLanguage(English);

msg.setOntology(Weather-Forecast-Ontology);

msg.setContent(Today its raining);

send(msg);

ACLMessage msg = receive();

if (msg != null) {

// Process the message

}

Sending a message is as simple as creating anSending a message is as simple as creating anSending a message is as simple as creating anSending a message is as simple as creating anACLMessage objectobjectobjectobject

and calling theand calling theand calling theand calling the send() method of themethod of themethod of themethod of theAgent classclassclassclass

Reading messages from the private message queue is accomplishedReading messages from the private message queue is accomplishedReading messages from the private message queue is accomplishedReading messages from the private message queue is accomplished

through thethrough thethrough thethrough the receive() method of themethod of themethod of themethod of theAgent class.class.class.class.

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Blocking a behaviour waiting for a message

public void action() {

ACLMessage msg = myAgent.receive();

if (msg != null) {

// Process the message

}else {

block();

}}

This is the strongly

recommended

pattern to receivemessages within abehaviour

AAAA behaviourbehaviourbehaviourbehaviour that processes incoming messages does not know exactlythat processes incoming messages does not know exactlythat processes incoming messages does not know exactlythat processes incoming messages does not know exactly

when a message will arrivewhen a message will arrivewhen a message will arrivewhen a message will arrive

TheTheTheTheblock() method of themethod of themethod of themethod of the Behaviour class removes aclass removes aclass removes aclass removes a behaviourbehaviourbehaviourbehaviourfrom the agent pool and puts it in a blocked state (from the agent pool and puts it in a blocked state (from the agent pool and puts it in a blocked state (from the agent pool and puts it in a blocked state (not a blocking call!!not a blocking call!!not a blocking call!!not a blocking call!!).).).).

Each time a message is received all blockedEach time a message is received all blockedEach time a message is received all blockedEach time a message is received all blocked behavioursbehavioursbehavioursbehaviours are insertedare insertedare insertedare inserted

back in the pool and have a chance to read and process the messaback in the pool and have a chance to read and process the messaback in the pool and have a chance to read and process the messaback in the pool and have a chance to read and process the message.ge.ge.ge.

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MessageTemplate tpl = MessageTemplate.MatchOntology(Test-Ontology);

public void action() {

ACLMessage msg = myAgent.receive(tpl);

if (msg != null) {// Process the message

}

else {

block();

}

}

Selective reading from the message queue

TheTheTheThe receive() method returns the first message in the messagemethod returns the first message in the messagemethod returns the first message in the messagemethod returns the first message in the message

queue and removes it.queue and removes it.queue and removes it.queue and removes it.

If there are two (or more)If there are two (or more)If there are two (or more)If there are two (or more) behavioursbehavioursbehavioursbehaviours receiving messages, one mayreceiving messages, one mayreceiving messages, one mayreceiving messages, one may

stealstealstealsteal a message that the other one was interested in.a message that the other one was interested in.a message that the other one was interested in.a message that the other one was interested in.

To avoid this it is possible to read only messages with certainTo avoid this it is possible to read only messages with certainTo avoid this it is possible to read only messages with certainTo avoid this it is possible to read only messages with certain

characteristics (e.g. whose sender is agentcharacteristics (e.g. whose sender is agentcharacteristics (e.g. whose sender is agentcharacteristics (e.g. whose sender is agent PeterPeterPeterPeter) specifying a) specifying a) specifying a) specifying a

jade.lang.acl.MessageTemplate parameter in theparameter in theparameter in theparameter in the receive()

method.method.method.method.

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Receiving messages in blocking mode

- Use receive() + Behaviour.block() to

receive messages within behaviours.- UseblockingReceive() to receive messageswithin the agent setup() and takeDown()

methods.

TheTheTheTheAgent class also provides theclass also provides theclass also provides theclass also provides theblockingReceive() method thatmethod thatmethod thatmethod that

returns only when there is a message in the message queue.returns only when there is a message in the message queue.returns only when there is a message in the message queue.returns only when there is a message in the message queue.

There areThere areThere areThere are overloaded versionsoverloaded versionsoverloaded versionsoverloaded versions that accept athat accept athat accept athat accept aMessageTemplate (the(the(the(themethod returns only when there is a message matching the templatmethod returns only when there is a message matching the templatmethod returns only when there is a message matching the templatmethod returns only when there is a message matching the template)e)e)e)

and or a timeout (if it expires the method returns null).and or a timeout (if it expires the method returns null).and or a timeout (if it expires the method returns null).and or a timeout (if it expires the method returns null).

Since it is a blocking call it isSince it is a blocking call it isSince it is a blocking call it isSince it is a blocking call it is dangerousdangerousdangerousdangerous to useto useto useto use

blockingReceive() within awithin awithin awithin a behaviourbehaviourbehaviourbehaviour. In fact no other. In fact no other. In fact no other. In fact no other behaviourbehaviourbehaviourbehaviour

can run untilcan run untilcan run untilcan run untilblockingReceive() returns.returns.returns.returns.

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Agenda

Overview

Creating Agents

Agent tasks

Agent communication

The yellow pages service

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The yellow pages service

A1: - serviceX

- serviceY

A2: - serviceZ

A3: - serviceW

- serviceK

- serviceH

Yellow Pages service

Publishprovidedservices

A1

A2

A3

A4

A5

A6

Search foragents

providing the

requiredservices

Exploit requiredservice

DF

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Interacting with the DF Agent

The DF is an agent and as such it communicates using ACLThe DF is an agent and as such it communicates using ACLThe DF is an agent and as such it communicates using ACLThe DF is an agent and as such it communicates using ACL

The ontology and language that the DFThe ontology and language that the DFThe ontology and language that the DFThe ontology and language that the DF understandsunderstandsunderstandsunderstands are specified byare specified byare specified byare specified by

FIPAFIPAFIPAFIPA It is possible to search/register to a DF agent of a remoteIt is possible to search/register to a DF agent of a remoteIt is possible to search/register to a DF agent of a remoteIt is possible to search/register to a DF agent of a remoteplatform.platform.platform.platform.

TheTheTheThe jade.domain.DFService class provides static utility methodsclass provides static utility methodsclass provides static utility methodsclass provides static utility methods

that facilitate the interactions with the DFthat facilitate the interactions with the DFthat facilitate the interactions with the DFthat facilitate the interactions with the DF

register();

modify();

deregister();

search();

The JADE DF also supports a subscription mechanismThe JADE DF also supports a subscription mechanismThe JADE DF also supports a subscription mechanismThe JADE DF also supports a subscription mechanism

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DFDescription format

When an agent registers with the DF it must provide a descriptioWhen an agent registers with the DF it must provide a descriptioWhen an agent registers with the DF it must provide a descriptioWhen an agent registers with the DF it must provide a descriptionnnn

(implemented by the(implemented by the(implemented by the(implemented by thejade.domain.FIPAAgentManagement.DFAgentDescription

class) basically composed ofclass) basically composed ofclass) basically composed ofclass) basically composed of The agent AID

A collection of service descriptions (implemented by the classServiceDescription). This, on its turn, includes:

The service type (e.g. Weather forecast);

The service name (e.g. Meteo-1);

The languages, ontologies and interaction protocols that must be known to

exploit the service

A collection of service-specific properties in the form key-value pair

When an agent searches/subscribes to the DF it must specify anotWhen an agent searches/subscribes to the DF it must specify anotWhen an agent searches/subscribes to the DF it must specify anotWhen an agent searches/subscribes to the DF it must specify anotherherherherDFAgentDescription that is used as a templatethat is used as a templatethat is used as a templatethat is used as a template