Artificial Intelligence Overview

John Paxton

Montana State University

August 14, 2003

Montana State University

A Brief Bio

• 1985 The Ohio State University, B.S.Computer Science

• 1987 The University of Michigan, M.S.Computer Science

• 1990 The University of Michigan, Ph.D.Artificial Intelligence

• 2003 Montana State University – Bozeman, Professor of Computer Science

Talk Outline

• What is AI?

• Foundations

• History

• Areas

• Search

• Knowledge Representation

• Agents

What is AI?

Science Approach

1. Systems that think like humans

2. Systems that act like humans

Engineering Approach

1. Systems that think rationally

2. Systems that act rationally

Acting Humanly

• Turing Test (1950)

Thinking Humanly

• Cognitive Modelling Approach

• General Problem Solver (Newell and Simon, 1961)

Thinking Rationally

• The laws-of-thought approach

• Syllogisms (Aristotle)

• It is difficult to code the knowledge and to reason with it efficiently.

Acting Rationally

• Rational Agent Approach. The agent acts to achieve the best (or near best) expected outcome.

Foundations

• Philosophy (e.g. Where does knowledge come from?)

• Mathematics (e.g. What are the formal rules to draw valid conclusions?)

• Economics (e.g. How should we make decisions to maximize payoff?)

• Neuroscience (e.g. How do brains process information?)

Foundations

• Psychology (e.g. How do humans and animals think and act?)

• Computer Engineering (e.g. How can we build an efficient computer?)

• Control Theory (e.g. How can artifacts operate under their own control?)

• Linguistics (e.g. How does language relate to thought?)

History

• 1943-1955 Gestation.McCulloch-Pitts, Hebb, Turing Test

• 1956. Dartmouth Conference. • 1952-1969. Great Expectations.

Logic Theorist, GPS, Checkers, Lisp, Microworlds (calculus)

• 1966-1973. Reality. Machine translation (spirit == vodka), chess, intractability, fundamental limitations (Perceptrons).

History

• 1969-1979. Knowledge-Based Systems. Dendral (infer molecular structure)

• 1980-present. Commercial Products.

• 1986-present. Return of neural networks.

• 1987-present. Science. Hidden Markov Models. Neural Networks. Bayesian Networks.

• 1995-present. Intelligent Agents.

Areas

• Agents

• Artificial Life

• Machine Discovery and Data Mining

• Expert Systems

• Fuzzy Logic

• Game Playing

• Genetic Algorithms

Areas

• Knowledge Representation

• Learning

• Neural Networks

• Natural Language Processing

• Planning

• Reasoning

• Robotics

Areas

• Search

• Speech Recognition and Synthesis

• Virtual Reality

• Computer Vision

Search

• Missionaries and Cannibals Problem

MMMCCC

Search

• Missionaries and Cannibals Solution

MMMCCC

MMCC

MC CMMM

CCMMM CCC

MMMC CC

MC

MMCC

MMCC

MC CC

MMMC

Types of Search

• Blind Search– Breadth-First Search– Depth-First Search

• Informed Search– Best-First Search– A* Search

Breadth-First Search

MMMCCC

MMMCC C

MMMC CC

MMCC

MC

Minimax Search

• Commonly used to determine which move to make in a 2 player, strategy game.

• Deep Junior (Ban, Bushinsky, Alterman), the reigning computer chess champion uses minimax.

• Minimax requires an evaluation function.

Minimax Example

• Nim

4 (my move)

3 2 1 (your move)

2 1 1 1 (my move)

1 (your move)

Chess Example

*

* * *

3 0 -5 4 10 2

maximizer

minimizer

Knowledge Representation

• Semantic Nets

• Fuzzy Logic

• First Order Predicate Calculus

Semantic Nets

bird

robin magpie ostrich

yes

no

is-ais-a

is-a

can-fly

can-fly

Fuzzy Logic

• Shaquille O’Neal is tall

5’0 6’0 7’0

tall

1.0

0.0

Fuzzy Logic

• Karim is tall (0.6) and a good teacher (0.9) = 0.6

• Karim is tall or a good teacher = 0.9.

• Karim is not tall = 1.0 – 0.6 = 0.4

First Order Predicate Calculus

• Every Saturday is a weekend.x Saturday(x) weekend(x)

• Some day is a week day.x day(x) weekday(x)

Agents

AGENT ENVIRONMENT

sensors

actuators

Rationality Factors

• Performance Measure

• Prior Knowledge

• Performable Actions

• Agent’s Prior Percepts

Rational Agent

• For each possible sensor sequence, a rational agent should select an action that is expected to maximize its performance measure, given the evidence provided by the sensor sequence and whatever built-in knowledge the agent has.

Agent Terminology

• Omniscience: the outcome of its actions are known. Impossible!

• Learning: taking actions in order to perform better (e.g. robot vacuum cleaner)

• Autonomy: the agent relies on its own sensors rather than built-in knowledge

Environments

• Fully observable vs. partially observable

• Deterministic vs. stochastic

• Episodic (classification) vs. sequential (conversation)

• Static vs. dynamic

• Discrete (chess) vs. continuous (taxi-driving)

• Single agent vs. multi-agent.

Types of Agents

• Reflex

• Model-Based

• Goal-Based

• Utility-Based

• Learning

• Combinations of the above!

Questions?