Transcript Introduction to Artificial Intelligence

For Friday
• No reading (other than handout)
• Homework:
– Chapter 2, exercises 5 and 6
– Lisp handout 1
What Do You Know?
• Examples of artificial intelligence in your
life?
Views of AI
• Weak vs. strong
• Scruffy vs. neat
• Engineering vs. cognitive
What Is an Agent?
• In this course (and your textbook):
– An agent can be viewed as perceiving its
environment
• Note that perception and environment may be very
limited
– An agent can be viewed as acting upon it
environment (presumably in response to its
perceptions)
• Agent is a popular term with nebulous
meaning--so don’t expect it to mean the
same thing all of the time in the literature
Rational Agents
• Organizing principle of textbook
• A rational agent is one that chooses the best
action based on its perceptions
• This does not have to be the best action that
could have been taken--perception may be
limited
Determining Rationality
• Must have a performance measure.
• Rationality depends on
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The performance measure.
Agent’s prior knowledge.
Agent’s possible actions.
Agent’s percept sequence to date.
Issues in Determining Rationality
• Omniscience
• Autonomy
Task Environment Specification
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Performance measure
Environment
Actuators
Sensors
Environment Issues
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Observability
Deterministic or stochastic
Episodic or not
Static or dynamic
Discrete or continuous
Single or multi-agent
Types of Agents
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Simple Reflex
Model-based Reflex
Goal-based
Utility-based
• Learning
LISP
• LISt Processing
• Functional Language
– Pure LISP doesn’t use things like assignment
statements or other imperative statements
(though LISP does have extensions that allow
you to use such techniques)
• Typically run in an interactive environment
Running LISP
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Log in to one of the Suns
At the prompt, type clisp
You’re now in a LISP environment
To get out: type (QUIT)
clisp is available for DOS and linux
The Lisp Interpreter
• When you start Lisp, you’re in an
interpreter
• Anytime you type something in, Lisp
assumes that you want it to evaluate what
you just typed
• What Lisp does depends on what you typed
Atoms
• The simplest thing in Lisp is an atom
• Numbers are atoms
• Anything that would be a standard identifier
in C++, etc., is also an atom.
• But alphanumeric atoms must be quoted
when we refer to them (otherwise Lisp
assume that they are variable names and
tries to evaluate them by finding their
contents--which may not exist)
Evaluating Atoms
>9
9
> abc
*** - EVAL: variable ABC has no value
> 32.0
32.0
> 'abc
ABC
> 43.2e02
4320.0
> 'fred
FRED
> 1000000000000
1000000000000
> 'H2O
H2O
Lists
• Lists are the crucial data structure in LISP
• They look like a list of atoms (or lists)
enclosed in parentheses:
(a b c 24 (a b))
• The list above has 5 members, one of them
a list with two members
• Like alphanumeric atoms, lists must be
quoted when you type them in to the
interpreter to keep Lisp from evaluating
them
nil
• nil or () is the empty list
• It is the only item in Lisp which is both an
atom and a list (at the same time)
• It is also Lisp’s value for FALSE (just like 0
is the value for FALSE in C and C++
• Note that Lisp also has a value for true: it is
t
More Examples
> '(a b c)
(A B C)
> ()
NIL
• Note that Lisp is not case sensitive. clisp
echoes everything in uppercase. Some
Lisps use lower case.
Function Calls in Lisp
• (functionname parameter1 parameter2 ...)
• (+ 3 5)
• All functions return values