Artificial Intelligence: Definition

“... the branch of computer science that is

concerned with the automation of intelligent

behavior.” (Luger, 2009)“The science and engineering of making intelligent

machines” (McCarthy, 2007)“The art of creating machines that perform

functions that require intelligence when performed

by people” (Kurzweil, 1990)

Artificial Intelligence: Definition

What is Intelligence?Is intelligence monolithic or diverse?Is there a range of intelligences?Must one be human to be intelligence?

What is artificial?Computers? Simulations?

Is there a difference between thinking intelligently

and acting intelligently?

Acting Humanly

The Turing Test: A

human judge converses

with a human and a

machine that pretends

to be human in natural

language .

Thinking Humanly

The machine thinks in the same way as a human,

passes psychological tests.Must it have the same sensory capability?Does this require simulation of the brain?Should the machine have the same limitations as a

human?

Cognitive Science, Neural Net Simulations

Acting Rationally

Rational Agent:Interacts with environmentHas goal or goals to achieveMeasured against optimal results (infinite

computational ability, omniscience)

Thinking Rationally

Formal reasoningLogic: Proposition, Predicate, Non-monotonic,

TemporalMathematical DeductionComputational LimitationsFocus on Reasoning, not Knowledge

Early Work

Focused on rules, game-playing, heuristicsGame Playing: CheckersGPS (General Problem Solver)SHRDLU (Block world)PerceptronsResolutionSIR (Question Answering)LADDER (Natural Language front-end for DBs)

Paradigm Shift

“Knowledge is power”Expert SystemsIncorporate knowledge from domain expertsKnowledge base more important, deduction engine

less importantIntroduce and measure uncertainty

Key Areas

DeductionSearchKnowledge RepresentationPerceptionPlanning LearningNatural LanguageRobotics

Approaches

SymbolistLogicRule-Based, Case-Based

Sub-SymbolistNeural NetsCognitive Simulation

StochasticBayesian Belief NetworksMarkov Chain Monte Carlo

Philosophical Issues

Can only humans think?Asking if machines can think is like asking if

submarines can swim (Minsky)If computers can only following their programming,

how can they be creative?Must machines think like humans?Ethic questions

Propositional Calculus

Propositions are statements that must be true or

false - “It is raining” “George W. Bush is President”Sufficient context is assumed to make statements

unambiguous (now, of the US...)Propositions are represented by letters, P, Q, R, S...May be combine by Boolean operators to make

more complex statements (formulas)

Boolean Operators

¬ Negation, not⋀ Conjunction, and⋁ Disjunction, or→ Implication, if then↔ Double implication, if and only if⊗ Exclusive Or

Negation is a unary operation, all others are binary.

Propositional Calculus - Syntax

Proposition symbols: P, Q, R, S (variables whose

values are true or false)Truth symbols: true, falseWell-formed formula (WFF): A proposition

symbol, truth value, or (¬ formula), or (formula op

formula) where op is one of ⋀, ⋁, →, ↔,⊗.These are the only formulas.

Propositional Calculus - Syntax

Order of precedence:

The operators have different levels of precedence

with negation binding more tightly, and exclusive

or least tightly (in the order given on a previous

slide).

We only use parentheses to change the normal order

of precedence.

Propositional Calculus - Semantics

An interpretation assigns a truth value (T or F) to

each propositional symbol in a formula.Formulas are evaluated recursively:

A propositional symbol's value is given by the

interpretationA truth symbol's value is T for true and F for falseFor a complex formula, first evaluation the

operand(s) and then apply the operator according

to its truth table.

Truth Tables

P QT T TT F F F T FF F F

P∧Q P Q P∨QT T TT F T F T TF F F

P QT T TT F F F T TF F T

P→Q

P QT T FT F T F T TF F F

P⊗QP ⌐PT FF T