Lecture Notes - Fri Jan 31

• Walk through chapter 2
  • rational agent : architecture + program
    • percept (input)
    • action (output)
  • performance measures
  • types of environments
    • fully vs partially observable
    • deterministic vs strategic vs stochastic
    • episodic vs sequential
    • static vs semidynamic vs dynamic
    • discrete vs continuous
    • single vs multi-agent
  • algorithms - how does it decide what to do?
    • random
    • table lookup
    • reflex (if ... then ...)
    • utility (maximize happiness) or goal search
    • learning (self-modifying)
    • history and world model (state)
    • some combination of all of the above

• a softbot system has
  • code for its environment
  • code for running and testing it
  • code for agent(s)
  • documentation and version history
  • So write one this weekend for the vacuum world

• textbook lisp vacuum world
  • Overview of AIMA Code
    • User's Guide
    • Agents
  • How to run it.

     [you@yourComputer]$ ssh you@cs.marlboro.edu
     [you@cs you]$  cd /usr/local/apache/htdocs/term/spring03/
     [you@cs you]$  cd ai-stuff/textbook-lisp-code/
     [you@cs you]$  lisp -quiet
     * (load "aima.lisp")
     T
     * (aima-load 'agents)
     T
     * (test 'agents)
     ... it prints a bunch of stuff ...
    

  • interface and assumptions
    • 2-dimensional 8x8 grid
    • percept: (bump dirt home), each a binary choice
    • actions: turnRight, turnLeft, forward, suck, nothing
    • performance measure
      • 100 points for each dirt vacuumed
      • -1 point for each step taken
      • -1000 points if it does not return home

• Lisp tidbits for the day
  • a few list and symbol operations

    	    
     (setf people '(jon mary ringo))
     people
     (first people)
     (rest people)
     (cons   '(a b c) '(d e f))
     (append '(a b c) '(d e f))
     (list   '(a b c) '(d e f))
     (push 'frank people)
     people
     (setf folks (pop (pop people)))
     people
     (length people)
    

  • Packages
    • namespace mechanism
    • global variable *package* is current package
    • foo:bar means symbol bar in package foo
    • foo::bar is same for "internal" (i.e. private) symbols
    • :bar is a symbol in the current package which evaluates to itself.
    • #:bar "when read, creates a unew uninterened symbol named BAR. Printed when the symbo bar is uninerned, i.e.has no home package."
    • Having fun at the interpreter

       * (eval *package*)
       * (eval :jim)
       * (list-all-packages)
       

    • an example from CCL2

       (cl:defpackage "MY-VERY-OWN-PACKAGE" 
        (:size 496) 
        (:nicknames "MY-PKG" "MYPKG" "MVOP") 
        (:use "COMMON-LISP") 
        (:shadow "CAR" "CDR") 
        (:shadowing-import-from "BRAND-X-LISP" "CONS") 
        (:import-from "BRAND-X-LISP" "GC" "BLINK-FRONT-PANEL-LIGHTS") 
        (:export "EQ" "CONS" "MY-VERY-OWN-FUNCTION"))
      

    • more examples from CCL2 (Common Lisp the Language, 2nd ed)
    • See CLL2 chap 11 for the full skinny.

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  Jim Mahoney (mahoney@marlboro.edu)
  Last modified: Fri Jan 31 12:50:02 EST 2003