Conception de modèles pour la simulation

Exercices de familiarisation

How does one program a Mas?

Methodology

– Internal structure of the agents

– Communication

– Control

Communication

• Questions – Who communicate with whom? – What language?

Coordination and control

• Questions – Who does what ? – How are the actions scheduled ? – How are the conflicts resolved ?

Without communication

• Planes coordinate without communication.

B: conflict with C

C: conflict with B

B: I go up

C: I stabilize the level

A: Conflict with B A: I turn right

B Conflict with A B: I turn right

With communication

A: I go to Montpellier

B I go to Chiang Mai

C: I go to Djakarta

B: Do I go up?

A: No you go left , I go up

B: ok

Without communication

• Agent structure

Sensors

Plan generator

Models of the world

Model assesment Controler

Environmental change

Possible plans Execution

With communication

Sensors

Plan generator

Models of the world

Model assesment Controler

Environmental change

Possible plans Execution

Communication

Planes

Three main issues for reactive agents

• Representation of space and environment

• Actions and perceptions

• Decision between perception and action

Environment

• A space and a medium for interactions

• The perception of an agent is the result of the actions of other agents (externalities)

Interactions

• Interactions through a field of forces

• Interactions through the use of marks

• Interactions through actions with neighbors

A field of forces

• Reynolds Boids

• Fish shoal (Mesle)

• Planes (Zeghal)

The use of marks

• The relation with environment is linked to the perception of marks,

• The action is the use of marks

• Examples

– Foraging robots

– Foraging ants

Without cooperation

• Explore : randomly

• Find : if I perceive a mine, then I take

• Carry: go back to the base

• Base : drop what I am carrying

With marks

• Robots use marks

• Follow Mark : If not carrying and perceive mark then follow marks

Result

With explicit cooperation

• Help: if perceive agent carrying then propose help

• Exchange : If help proposed then give the resource

Action on the neighbors

• Assess the state of the neighbors and the pressure

• Analyze the state and pressure and choose the best action

• Move and put pressure on the neighbours

Cognitive agents

• A cognitive agent– has memory– has beliefs and skills– has goals– can communicate

• Some parts of knowledge are facts. Other parts are models of the world.

Three main questions for a cognitive MAS

• Decision

• Organization

• Communication

Decision

• Choices– Knowledge and beliefs

– Objectives

– Computation

• What are the formalisms?

Organization

• Who can do the task ?

• Who has access to resources ?

• Who can communicate ?

Communication

• Agents communicate

– to inform themselves

– to distribute the tasks

– to resolve the conflicts

– to learn

• The problem of languages

From goals to intentions (commitment)

• Blinded : Until the agent believes it has accomplished its intention

• Single-minded : As long as it thinks it is possible

• Open minded : As soon as it has the goal

Some strategies for negotiation

• Always concede

• Be competitive

• Be cooperative : look for a mutually acceptable solution

• Inaction

• Break

From individual to collective with cognitive agents.

• Reactive agents often coordinate through the environment

• Two approaches for cognitive agents – define mutual beliefs, joint desires and joint

intentions – define norms and conventions.