1. January 11, 2006AI: Chapter 2: Intelligent Agents1 Artificial Intelligence Chapter 2: Intelligent Agents Michael Scherger Department of Computer Science Kent State University

2. January 11, 2006AI: Chapter 2: Intelligent Agents2 Agents and Environments An Agent is anything that can be viewed as perceiving its environment through sensors and acting upon that environment through actuators Agent Environment Percepts Actions ? Sensors Actuators

3. January 11, 2006AI: Chapter 2: Intelligent Agents3 Agents and Environments Percept – the agent’s perceptual inputs –percept sequence is a sequence of everything the agent has ever perceived Agent Function – describes the agent’s behavior –Maps any given percept sequence to an action –f : P* -> A Agent Program – an implementation of an agent function for an artificial agent

4. January 11, 2006AI: Chapter 2: Intelligent Agents4 Agents and Environments Example: Vacuum Cleaner World –Two locations: squares A and B –Perceives what square it is in –Perceives if there is dirt in the current square –Actions move left move right suck up the dirt do nothing AB

5. January 11, 2006AI: Chapter 2: Intelligent Agents5 Agents and Environments Agent Function: Vacuum Cleaner World –If the current square is dirty, then suck, otherwise move to the other square Percept SequenceAction [A, Clean]Right [A, Dirty]Suck [B, Clean]Left [B, Dirty]Suck [A, Clean], [A, Clean]Right [A, Clean], [A, Dirty]Suck

6. January 11, 2006AI: Chapter 2: Intelligent Agents6 Agents and Environments But what is the right way to fill out the table? –is the agent good or bad intelligent or stupid –can it be implemented in a small program? Function Reflex-Vacuum-Agent([location, status]) return an action if status == Dirty then return Suck else if location = A then return Right else if location = B then return Left

7. January 11, 2006AI: Chapter 2: Intelligent Agents7 Good Behavior and Rationality Rational Agent – an agent that does the “right” thing –Every entry in the table for the agent function is filled out correctly –Doing the right thing is better than doing the wrong thing What does it mean to do the right thing?

8. January 11, 2006AI: Chapter 2: Intelligent Agents8 Good Behavior and Rationality Performance Measure –A scoring function for evaluating the environment space Rational Agent – 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 what ever built-in knowledge the agent has.

9. January 11, 2006AI: Chapter 2: Intelligent Agents9 Good Behavior and Rationality Rational != omniscient Rational != clairvoyant Rational != successful Rational -> exploration, learning, autonomy

10. January 11, 2006AI: Chapter 2: Intelligent Agents10 The Nature of Environments Task environments –The “problems” to which a rational agent is the “solution” PEAS –Performance –Environment –Actuators –Sensors

11. January 11, 2006AI: Chapter 2: Intelligent Agents11 The Nature of Environments Properties of task environments –Fully Observable vs. Partially Observable –Deterministic vs. Stochastic –Episodic vs. Sequential –Static vs. Dynamic –Discrete vs. Continuous –Single agent vs. Multi-agent The real world is partially observable, stochastic, sequential, dynamic, continuous, multi-agent

12. January 11, 2006AI: Chapter 2: Intelligent Agents12 The Nature of Environments Examples –Solitaire –Backgammon –Automated Taxi –Mars Rover

13. January 11, 2006AI: Chapter 2: Intelligent Agents13 The Structure of Agents Agent = Architecture + Program Basic algorithm for a rational agent –While (true) do Get percept from sensors into memory Determine best action based on memory Record action in memory Perform action Most AI programs are a variation of this theme

14. January 11, 2006AI: Chapter 2: Intelligent Agents14 The Structure of Agents Table Driven Agent function Table-Driven-Agent (percept) return action static:percepts, a sequence, initially empty table, a table of actions, indexed by percept sequences, initially fully specified append percept to the end of the table action <- LOOKUP( percept, table ) return action

15. January 11, 2006AI: Chapter 2: Intelligent Agents15 The Structure of Agents Simple Reflex Agent Environment Percepts Actions What the world is like now Sensors Actuators What action I should do now Condition-Action Rules

16. January 11, 2006AI: Chapter 2: Intelligent Agents16 The Structure of Agents Simple Reflex Agent function Simple-Reflex-Agent (percept) return action static:rules, a set of condition-action rules state <- INTERPRET-INPUT( percept ) rule <- RULE-MATCH( state, rules ) action <- RULE-ACTION[ rule ] return action

17. January 11, 2006AI: Chapter 2: Intelligent Agents17 The Structure of Agents Reflex Agent With State Environment Percepts Actions What the world is like now Sensors Actuators What action I should do now Condition-Action Rules State How the world evolves What my actions do

18. January 11, 2006AI: Chapter 2: Intelligent Agents18 The Structure of Agents Reflex Agent With State function Reflex-Agent-With-State (percept) return action static: state, a description of the current world state rules, a set of condition-action rules action, the most recent action, initially none state <- UPDATE-STATE( state, action, percept ) rule <- RULE-MATCH( state, rules ) action <- RULE-ACTION[ rule ] return action

19. January 11, 2006AI: Chapter 2: Intelligent Agents19 The Structure of Agents Goal Based Agent Environment Percepts Actions What the world is like now Sensors Actuators What action I should do now Goals State How the world evolves What my actions do What it will be like if I do action A

20. January 11, 2006AI: Chapter 2: Intelligent Agents20 The Structure of Agents Utility Based Agent Environment Percepts Actions What the world is like now Sensors Actuators What action I should do now Utility State How the world evolves What my actions do What it will be like if I do action A How happy I will be in such a state

21. January 11, 2006AI: Chapter 2: Intelligent Agents21 The Structure of Agents Learning Based Agent Environment Percepts Actions Critic (external performance standard) Sensors Actuators Performance Element Learning Element Problem Generator changes knowledge feedback learning goals