Transcript beekman7_ppt_15

Computer
Confluence 7/e
© 2006 Prentice-Hall, Inc.
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Computer Confluence 7/e
Chapter 15
Is Artificial Intelligence Real?
© 2006 Prentice-Hall, Inc.
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Chapter 15
Objectives
Explain the two basic approaches of artificial intelligence
research
Describe several hard problems that artificial intelligence
research has not been able to solve yet
Describe several practical applications of artificial intelligence
Explain what robots are and give several examples illustrating
what they can—and can’t—do
© 2006 Prentice-Hall, Inc.
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Chapter 15
Alan Turing, Military Intelligence, and Intelligent
Machines
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Alan M. Turing was the British mathematician who designed
the world’s first operational electronic digital computer during
the 1940s:
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Turing effectively launched the field of artificial intelligence (AI) with
a 1950 paper called “Computing Machinery and Intelligence”
In 1952 he was professionally and socially devastated when he was
arrested and injected with hormones for violation of British antihomosexuality laws
The 41-year-old genius apparently committed suicide in 1954, years
before the government made his wartime heroics public
Four decades after his death, Turing’s work still has relevance to
computer scientists, mathematicians, and philosophers
© 2006 Prentice-Hall, Inc.
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Chapter 15
Thinking about Thinking Machines
Can Machines Think?
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The Turing test:
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Involves two people and a computer
One person, the interrogator, sits at a terminal and types questions
The questions can be about anything—math, science, politics, sports,
entertainment, art, human relationships, emotions, etc.
As answers to the questions asked appear on the screen, the
interrogator attempts to guess whether those answers were typed by the
other person or generated by the computer
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According to Turing, by repeatedly fooling interrogators into thinking it is
a person, a computer can demonstrate intelligent behavior. If it acts
intelligently, it is intelligent.
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
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Turing did not intend this test to be the only way to demonstrate machine
intelligence; he pointed out that a machine could fail and still be
intelligent
Even so, Turing believed that machines would be able to pass his test by
the turn of the century
So far no computer has come close, in spite of 40 years of AI research
While some people still cling to the Turing test to define artificial
intelligence, most AI researchers favor less stringent definitions
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
What Is Artificial Intelligence?
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Many computer scientists believe that if a task is easy to
perform with a computer, it can’t be artificial intelligence
More recent textbook definition that reflects this point of view:
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Artificial intelligence is the study of how to make computers do things at
which, at the moment, people are better. —Elaine Rich, in Artificial
Intelligence
Artificial intelligence is the study of the computations that make it
possible to perceive, reason, and act. —Patrick Henry Winston, in
Artificial Intelligence
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
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Two common approaches to AI
Use computers to simulate human mental processes.
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Three inherent problems:
Most people have trouble knowing and describing how they do things
Vast differences between the capabilities of the human brain and those of
a computer
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Even the most powerful supercomputers can’t approach the brain’s ability to
perform parallel processing
The best way to do something with a machine is often very different
from the way people would do it
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
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Designing intelligent machines independent of the way people
think
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A more common approach
Human intelligence is just one possible kind of intelligence
A machine’s method for solving a problem might be different from the
human method but no less intelligent
Many problems are far too complex to solve all at once
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Break these problems into smaller problems that are easier to solve
Create programs that can function intelligently when confined to limited
domains
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
Opening Games
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One of the first popular domains for AI research was the
checkerboard
AI techniques that are still used today in a variety of
applications:
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Searching: Looking ahead to the possibilities generated by each
potential move
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The staggering number of decision points makes brute-force searching
impractical
Generally guided by a planned strategy and by rules known as heuristics
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
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Heuristics: Rule of thumb
 Guide us toward judgments that experience tells us are likely to be
true
 For example, in checkers, “Keep checkers in the king’s row as long
as possible.”
Pattern recognition: identifying recurring patterns in input data
 Goal: understanding or categorizing that input
 The best human chess and checkers players remember thousands of
critical board patterns and know the best strategies for playing when
those patterns or similar patterns appear
 Game-playing programs recognize recurring patterns, too, but not
nearly as well as people do
© 2006 Prentice-Hall, Inc.
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Thinking about Thinking Machines
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Computer game programs often have trouble identifying situations
that are similar but not identical
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Pattern recognition is probably the single biggest advantage a human
game player has over a computer opponent
Machine learning: learn from experience
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If a move pays off, a learning program is more likely to use that
move (or similar moves) in future games
Most AI researchers have moved on to more interesting and practical
applications
© 2006 Prentice-Hall, Inc.
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Natural-Language Communication
Machine Translation Traps
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One early project attempted to create a program that could
translate scientific papers between English and Russian
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Automatic translation offered hope for increased communication between
scientists during the tense Cold War years
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A parsing program (parser) would analyze sentence structure
Identify each word by part of speech;
Look up each word in a translation dictionary and substitute the appropriate
word
After spending 15 years and millions of dollars on research, scientists
abandoned the project
© 2006 Prentice-Hall, Inc.
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Natural-Language Communication
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Conversation without Communication
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Joseph Weizenbaum, an MIT professor, designed ELIZA in the 1960s to
simulate the role of a therapist in a typed conversation with a patient
An ELIZA session can easily deteriorate into nonsense dialog laced with
grammatical errors and inappropriate responses
ELIZA doesn’t pass the Turing test
Nonsense and Common Sense
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Part of the problem with natural-language communications is the
massive vocabulary of natural languages
Natural-language parsing programs have to deal with rules that are
vague, ambiguous, and occasionally contradictory
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Natural-Language Communication
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Computers are far more successful dealing with natural-language
syntax than with semantics—the underlying meaning of words and
phrases
Computers lack what we call common sense—the wealth of
knowledge and understanding about the world that people share
The most successful natural-language applications limit the domain
so that virtually all relevant information can be fed to the system
Natural-language processing has come a long way since
ELIZA’s early conversations
Computers still can’t pass the Turing test, but they can at
least sometime fool people
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
Knowledge Bases
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AI researchers continue to develop techniques for
representing knowledge in computers
Knowledge base contains a system of rules for determining
and changing the relationship among facts in a database
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Facts stored in a database are rigidly organized into categories
Ideas stored in a knowledge base can be reorganized as new
information changes their relationships
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
Artificial Experts
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An expert system is designed to replicate the decision-making
process of a human expert
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Requires a knowledge base representing ideas from a specific field of
expertise
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Constructed by a user, an expert, or a knowledge engineer—a specialist who
converts the words and actions of experts into a knowledge base
Some new expert systems can grow their own knowledge bases while
observing human decision makers doing their jobs
For most expert systems, the process is still human intensive
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
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A complete expert system also includes:
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Roles of expert systems
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A human interface, which enables the user to interact with the system
An inference engine, which puts the user input together with the
knowledge base, applies logical principles, and produces the requested
expert advice
Aid experts by providing automated data analysis and informed second
opinions
Support non-experts by providing advice based on judgments of one or
more experts
Function within narrow, carefully defined domains
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
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Expert Systems in Action:
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The MYCIN medical expert system outperformed many human experts
in diagnosing diseases
XCON, one of the most successful expert systems in commercial use
today, has been configuring complex computer systems since it was
developed at Digital Equipment Corporation in 1980
American Express uses an expert system to automate the process of
checking for fraud and misuses of its no-limit credit card
Blue Cross/Blue Shield of Virginia uses an expert system to automate
insurance claim processing
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
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Boeing Company factory workers use an expert system to locate the
right parts, tools, and techniques for assembling airplane electrical
connectors
AARON, an automated artist programmed by Harold Cohen—an artist
and professor at the University of California at San Diego—uses more
than 1,000 rules of human anatomy and behavior to create drawings of
people, plants, and abstract objects with a robotic drawing machine
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Knowledge Bases and Expert Systems
Expert Systems in Perspective
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An expert system can perform these tasks:
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Help train new employees
Reduce the number of human errors
Take care of routine tasks so workers can focus on more challenging
jobs
Provide expertise when no experts are available
Preserve the knowledge of experts after those experts leave an
organization
Combine the knowledge of several experts
Make knowledge available to more people
© 2006 Prentice-Hall, Inc.
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Knowledge Bases and Expert Systems
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Even with a knowledge base, an expert system isn’t the
machine equivalent of a human expert
Clearly, knowledge engineers can’t use rules to teach
computers all they need to know to perform useful, intelligent
functions outside narrow domains
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
Image Analysis
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Image analysis: the process of identifying objects and shapes
in a photograph, drawing, video, or other visual image
Used for everything from colorizing classic motion pictures to
piloting cruise missiles
Today’s PCs are capable of running image processing software
with practical applications
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Example: Security programs enable PCs with video cameras to
recognize faces of valid users with a high degree of reliability
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
Optical Character Recognition
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Optical character recognition (OCR) software locates and
identifies printed characters embedded in images, thereby
“reading” text
State-of-the-art OCR programs use several techniques:
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Segmentation of a page into pictures, text blocks, and (eventually)
individual characters
Scaled-down expert system technology for recognizing the underlying
rules that distinguish letters
Context “experts” to help identify ambiguous letters by their context
Learning from actual examples and feedback from a human trainer
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
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Today’s best programs can achieve up to 99% accuracy; they
can perform even better under optimal circumstances
OCR technology also can be applied to handwritten text, but
not as reliably
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
Automatic Speech Recognition
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Automatic speech recognition systems use pattern recognition
techniques similar to those used by vision and OCR systems,
including:
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Segmentation of input sound patterns into individual words and phonemes
Expert rules for interpreting sounds
Context “experts” for dealing with ambiguous sounds
Learning from a human trainer
Voice recognition systems with speaker independence—the
ability to recognize speech without being trained—are
becoming more common, making speech recognition practical
for more applications
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
Talking Computers
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Many computer applications speak like humans by playing
prerecorded digitized speech (along with other digitized
sounds) stored in memory or on disk
Recorded speech won’t work for applications in which the text
to be spoken is unpredictable—such as a talking word
processor—because all the sounds must be prerecorded
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These types of applications require text-to-speech conversion—the
creation of synthetic speech by converting text files into phonetic sounds
With speech synthesis software or hardware, PCs can recite anything
you can type, but with voices that sound artificial and robotic
© 2006 Prentice-Hall, Inc.
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Pattern Recognition: Making Sense of the World
Neural Networks
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Neural networks (or neural nets): distributed, parallel
computing systems
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Uses a network of a few thousand simpler processors called
neurons.
Not programmed in the usual way—they’re trained.
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Inspired by the structure of the human brain
Learns patterns by trial and error, just as the brain does.
Optimistic researchers hope that neural networks may someday
provide hearing for the deaf and eyesight for the blind
© 2006 Prentice-Hall, Inc.
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The Robot Revolution
What Is a Robot?
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A robot is a computer-controlled machine designed to perform
specific manual tasks
A robot’s central processor might be a microprocessor
embedded in the robot’s shell, or it might be a supervisory
computer that controls the robot from a distance.
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Functionally identical to the processor found in a computer.
The most important hardware differences between robots and
other computers are the input and output peripherals
© 2006 Prentice-Hall, Inc.
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The Robot Revolution
Steel-Collar Workers
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From a management point of view, robots offer several
advantages:
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Robots save labor costs
Robots can work 24 hours a day, 365 days a year, without vacations,
strikes, sick leave, or coffee breaks
Robots can also improve quality and increase productivity.
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They’re especially effective at doing repetitive jobs.
Robots are ideal for jobs that are dangerous, uncomfortable, or
impossible for human workers
© 2006 Prentice-Hall, Inc.
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AI Implications and Ethical Questions
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As it matures, AI technology finds its way out of the research
lab and into the marketplace
A growing number of programs and products incorporate pattern
recognition, expert systems, and other AI techniques
In the near future we’re likely to see more products with
embedded AI, including:
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Intelligent word processors that can help writers turn rough drafts into polished
prose
Smart appliances that can recognize and obey their owners’ spoken commands
Vehicles that can perform their own diagnostics and, in many cases, repairs
© 2006 Prentice-Hall, Inc.
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Lesson Summary
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Some AI researchers try to simulate human intelligent behavior,
but most try to design intelligent machines independent of the
way people think
Successful AI research generally involves working on problems
with limited domains rather than trying to tackle large, openended problems
AI programs employ a variety of techniques, including
searching, heuristics, pattern recognition, and machine learning,
to achieve their goals
AI researchers have developed a variety of schemes for
representing knowledge in computers
© 2006 Prentice-Hall, Inc.
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Lesson Summary (continued)
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We’ll also see more distributed intelligence —AI concepts
applied to networks rather than to individual computers
A robot is a computer-controlled machine designed to perform
specific manual tasks
As robot technology advances, artificial workers will do more
traditional human jobs
In spite of the numerous difficulties AI researchers encounter
when trying to produce truly intelligent machines, many experts
believe that people will eventually create artificial beings that are
more intelligent than their creators—a prospect with staggering
implications
© 2006 Prentice-Hall, Inc.
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