6 What is AI?Intelligence: “ability to learn, understand and think” (Oxford dictionary)AI is the study of how to make computers make things which at the moment people do better.Examples: Speech recognition, Smell, Face, Object, Intuition, Inferencing, Learning new skills, Decision making, Abstract thinking
7 What is AI? Thinking humanly Thinking rationally Acting humanly Acting rationally
8 Acting Humanly: The Turing Test Alan Turing ( )“Computing Machinery and Intelligence” (1950)Imitation GameHumanHuman InterrogatorAI System
9 Acting Humanly: The Turing Test Predicted that by 2000, a machine might have a 30% chance of fooling a lay person for 5 minutes.Anticipated all major arguments against AI infollowing 50 years.Suggested major components of AI: knowledge,reasoning, language, understanding, learning.
10 Thinking Humanly: Cognitive Modelling Not content to have a program correctly solving a problem.More concerned with comparing its reasoning stepsto traces of human solving the same problem.Requires testable theories of the workings of thehuman mind: cognitive science.
11 Thinking Rationally: Laws of Thought Aristotle was one of the first to attempt to codify “right thinking”, i.e., irrefutable reasoning processes.Formal logic provides a precise notation and rules for representing and reasoning with all kinds of things in the world.Obstacles:- Informal knowledge representation.- Computational complexity and resources.
12 Acting RationallyActing so as to achieve one’s goals, given one’s beliefs.Does not necessarily involve thinking.Advantages:- More general than the “laws of thought” approach.- More amenable to scientific development than human- based approaches.
13 The Foundations of AI Philosophy (423 BC - present): - Logic, methods of reasoning.- Mind as a physical system.- Foundations of learning, language, and rationality.Mathematics (c present):- Formal representation and proof.- Algorithms, computation, decidability, tractability.- Probability.
14 The Foundations of AI Psychology (1879 - present): - Adaptation. - Phenomena of perception and motor control.- Experimental techniques.Linguistics ( present):- Knowledge representation.- Grammar.
15 A Brief History of AI The gestation of AI (1943 - 1956): - 1943: McCulloch & Pitts: Boolean circuit model of brain.- 1950: Turing’s “Computing Machinery and Intelligence”.- 1956: McCarthy’s name “Artificial Intelligence” adopted.Early enthusiasm, great expectations ( ):- Early successful AI programs: Samuel’s checkers,Newell & Simon’s Logic Theorist, Gelernter’s GeometryTheorem Prover.- Robinson’s complete algorithm for logical reasoning.
16 A Brief History of AI A dose of reality (1966 - 1974): - AI discovered computational complexity.- Neural network research almost disappeared afterMinsky & Papert’s book in 1969.Knowledge-based systems ( ):- 1969: DENDRAL by Buchanan et al..- 1976: MYCIN by Shortliffle.- 1979: PROSPECTOR by Duda et al..
17 A Brief History of AI AI becomes an industry (1980 - 1988): - Expert systems industry booms.- 1981: Japan’s 10-year Fifth Generation project.The return of NNs and novel AI ( present):- Mid 80’s: Back-propagation learning algorithm reinvented.- Expert systems industry busts.- 1988: Resurgence of probability.- 1988: Novel AI (ALife, GAs, Soft Computing, …).- 1995: Agents everywhere.- 2003: Human-level AI back on the agenda.
18 Task Domains of AI Mundane Tasks: Formal Tasks Expert Tasks: PerceptionVisionSpeechNatural LanguagesUnderstandingGenerationTranslationCommon sense reasoningRobot ControlFormal TasksGames : chess, checkers etcMathematics: Geometry, logic,Proving properties of programsExpert Tasks:Engineering ( Design, Fault finding, Manufacturing planning)Scientific AnalysisMedical DiagnosisFinancial Analysis
19 AI Technique Intelligence requires Knowledge Knowledge posesses less desirable properties such as:VoluminousHard to characterize accuratelyConstantly changingDiffers from data that can be usedAI technique is a method that exploits knowledge that should be represented in such a way that:Knowledge captures generalizationIt can be understood by people who must provide itIt can be easily modified to correct errors.It can be used in variety of situations
20 The State of the Art Computer beats human in a chess game. Computer-human conversation using speech recognition.Expert system controls a spacecraft.Robot can walk on stairs and hold a cup of water.Language translation for webpages.Home appliances use fuzzy logic.......
21 Tic Tac Toe Three programs are presented : Series increase Their complexityUse of generalizationClarity of their knowledgeExtensability of their approach
23 Introductory Problem: Tic-Tac-Toe Program 1:Data Structures:Board: 9 element vector representing the board, with 1-9 for each square. An element contains the value 0 if it is blank, 1 if it is filled by X, or 2 if it is filled with a OMovetable: A large vector of 19,683 elements ( 3^9), each element is 9-element vector.Algorithm:1. View the vector as a ternary number. Convert it to adecimal number.2. Use the computed number as an index intoMove-Table and access the vector stored there.3. Set the new board to that vector.
24 Introductory Problem: Tic-Tac-Toe Comments:This program is very efficient in time.1. A lot of space to store the Move-Table.2. A lot of work to specify all the entries in theMove-Table.3. Difficult to extend.
26 Introductory Problem: Tic-Tac-Toe Program 2:Data Structure: A nine element vector representing the board. But instead of using 0,1 and 2 in each element, we store 2 for blank, 3 for X and 5 for OFunctions:Make2: returns 5 if the center sqaure is blank. Else any other balnk sqPosswin(p): Returns 0 if the player p cannot win on his next move; otherwise it returns the number of the square that constitutes a winning move. If the product is 18 (3x3x2), then X can win. If the product is 50 ( 5x5x2) then O can win.Go(n): Makes a move in the square nStrategy:Turn = 1 Go(1)Turn = 2 If Board is blank, Go(5), else Go(1)Turn = 3 If Board is blank, Go(9), else Go(3)Turn = 4 If Posswin(X) 0, then Go(Posswin(X))
27 Introductory Problem: Tic-Tac-Toe Comments:1. Not efficient in time, as it has to check severalconditions before making each move.2. Easier to understand the program’s strategy.3. Hard to generalize.
29 Introductory Problem: Tic-Tac-Toe Comments:1. Checking for a possible win is quicker.2. Human finds the row-scan approach easier, whilecomputer finds the number-counting approach moreefficient.
30 Introductory Problem: Tic-Tac-Toe Program 3:1. If it is a win, give it the highest rating.2. Otherwise, consider all the moves the opponentcould make next. Assume the opponent will makethe move that is worst for us. Assign the rating ofthat move to the current node.3. The best node is then the one with the highestrating.
31 Introductory Problem: Tic-Tac-Toe Comments:1. Require much more time to consider all possiblemoves.2. Could be extended to handle more complicatedgames.
32 Exercises 1. Characterize the definitions of AI: "The exciting new effort to make computers think ...machines with minds, in the full and literal senses"(Haugeland, 1985)"[The automation of] activities that we associate withhuman thinking, activities such as decision-making,problem solving, learning ..."(Bellman, 1978)
33 Exercises "The study of mental faculties, through the use of computational models"(Charniak and McDermott, 1985)"The study of the computations that make it possible toperceive, reason, and act"(Winston, 1992)"The art of creating machines that perform functions thatrequire intelligence when performed by people"(Kurzweil, 1990)
34 Exercises "The study of how to make computers do things at which, at the moment, people are better"(Rich and Knight, 1991)"A field of study that seeks to explain and emulateintelligent behavior in terms of computationl processes"(Schalkoff, 1990)"The branch of computer science that is concerned withthe automation of intelligent behaviour"(Luger and Stubblefield, 1993)
35 Exercises "A collection of algorithms that are computationally tractable, adequate approximations of intractabiliyspecified problems"(Partridge, 1991)"The enterprise of constructing a physical symbolsystem that can reliably pass the Turing test"(Ginsberge, 1993)"The f ield of computer science that studies howmachines can be made to act intelligently"(Jackson, 1986)