Lec 2 agents

Lec 2 agents

• 1.
  Intelligent Agents Lecture 2
• 2.
  Outline • Agents andenvironments • Rationality • PEAS (Performance measure, Environment, Actuators, Sensors) • Environment types • Agent types
• 3.
  Agents • An agentis anything that can be viewed as perceiving its environment through sensors and acting upon that environment through actuators • Human agent: – eyes, ears, and other organs for sensors; – hands, legs, mouth, and other body parts for actuators • Robotic agent: – cameras and infrared range finders for sensors; – various motors for actuators • Sofware agent: – Receives keystrokes, file contents and network packets as sensory inputs – Acts on environment by displaying on screen, writing files and sending network packets
• 4.
  Agents and Environments •The agent function maps from percept histories to actions: [f: P*  A] • The agent program runs on the physical architecture to produce f • agent = architecture + program
• 5.
  Example: Vacuum-cleaner world •Percepts: location and contents, e.g., [A,Dirty] • Actions: Left, Right, Suck, NoOp • Simple function: if current square is dirty, suck; otherwise, move to the other square.
• 6.
  Tabulation: vacuum-cleaner agent •What is the right way to fill the out the table? • What makes an agent good or bad, intelligent or stupid?
• 7.
  Rational agents • Anagent should strive to "do the right thing", based on what it can perceive and the actions it can perform. The right action is the one that will cause the agent to be most successful • Performance measure: An objective criterion for success of an agent's behavior • E.g., performance measure of a vacuum-cleaner agent could be amount of dirt cleaned up, amount of time taken, amount of electricity consumed, amount of noise generated, etc.
• 8.
  Rational agents • RationalAgent: For each possible percept sequence, a rational agent should select an action that is expected to maximize its performance measure, given the evidence provided by the percept sequence and whatever built-in knowledge the agent has.
• 9.
  Rational agents • Rationalityis distinct from omniscience (all- knowing with infinite knowledge). – Omniscient agent knows actual outcomes of its actions and act accordingly. • Agents can perform actions in order to modify future percepts so as to obtain useful information (information gathering, exploration). • An agent is autonomous if its behavior is determined by its own experience (with ability to learn and adapt).
• 10.
  PEAS • PEAS: Performancemeasure, Environment, Actuators, Sensors • Must first specify the setting for intelligent agent design • Consider, e.g., the task of designing an automated taxi driver: – Performance measure – Environment – Actuators – Sensors
• 11.
  PEAS • Must firstspecify the setting for intelligent agent design • Consider, e.g., the task of designing an automated taxi driver: – Performance measure: Safe, fast, legal, comfortable trip, maximize profits – Environment: Roads, other traffic, pedestrians, customers – Actuators: Steering wheel, accelerator, brake, signal, horn – Sensors: Cameras, sonar, speedometer, GPS, odometer, engine sensors, keyboard
• 12.
  PEAS • Agent: Medicaldiagnosis system • Performance measure: Healthy patient, minimize costs, lawsuits • Environment: Patient, hospital, staff • Actuators: Screen display (questions, tests, diagnoses, treatments, referrals) • Sensors: Keyboard (entry of symptoms, findings, patient's answers)
• 13.
  PEAS • Agent: Part-pickingrobot • Performance measure: Percentage of parts in correct bins • Environment: Conveyor belt with parts, bins • Actuators: Jointed arm and hand • Sensors: Camera, joint angle sensors
• 14.
  PEAS • Agent: InteractiveEnglish tutor • Performance measure: Maximize student's score on test • Environment: Set of students • Actuators: Screen display (exercises, suggestions, corrections) • Sensors: Keyboard
• 15.
  Environment types • Fullyobservable (vs. partially observable): An agent's sensors give it access to the complete state of the environment at each point in time. • Deterministic (vs. stochastic): The next state of the environment is completely determined by the current state and the action executed by the agent. (If the environment is deterministic except for the actions of other agents, then the environment is strategic) • Episodic (vs. sequential): The agent's experience is divided into atomic "episodes" (each episode consists of the agent perceiving and then performing a single action), and the choice of action in each episode depends only on the episode itself.
• 16.
  Environment types • Static(vs. dynamic): The environment is unchanged while an agent is deliberating. (The environment is semidynamic if the environment itself does not change with the passage of time but the agent's performance score does) • Discrete (vs. continuous): A limited number of distinct, clearly defined percepts and actions. • Single agent (vs. multiagent): An agent operating by itself in an environment.
• 17.
  Environment types Chess withChess without Taxi driving a clock a clock Fully observable Yes Yes No Deterministic Strategic Strategic No Episodic No No No Static Semi Yes No Discrete Yes Yes No Single agent No No No • The environment type largely determines the agent design • The real world is (of course) partially observable, stochastic, sequential, dynamic, continuous, multi-agent
• 18.
  Agent functions andprograms • An agent is completely specified by the agent function mapping percept sequences to actions • One agent function (or a small equivalence class) is rational • Aim: find a way to implement the rational agent function concisely
• 19.
  Table-lookup agent • Drawbacks: –Huge table – Take a long time to build the table – No autonomy – Even with learning, need a long time to learn the table entries
• 20.
  Agent program fora vacuum- cleaner agent
• 21.
  Agent types • Fourbasic types in order of increasing generality: • Simple reflex agents • Model-based reflex agents • Goal-based agents • Utility-based agents
• 22.
  Simple reflex agents Theseagents select actions on the basis of the current percept, ignoring the rest of the percept history.
• 23.
  Simple reflex agents
• 24.
  Model-based reflex agents
• 25.
  Model-based reflex agents •the agent should maintain some sort of internal state that depends on the percept history and thereby reflects at least some of the unobserved aspects of the current state.
• 26.
  Goal-based agents
• 27.
  Utility-based agents
• 28.
  Learning agents