QUIZ 4                         YOUR NAME:                    

Handed out/Assigned:	Tuesday, April 25, 2006
Due:	Thursday, April  27, 2006  in class

FROM THE TEXT:  Chapter 8,  (Read it!  It has lots of good stuff), pp. 137-138:  8.2  AND 8.5.

OUR VERY OWN PROBLEM:

•   Assume our original, 3 blocks BlocksWorld, in which the only operators are "move(column_num, left)" and "move(column_num, right)", and there are only three columns (numbers 0,1,2).
   "move(column_num, left)" would move the topmost block on the column in "column_num" to the top of the column to the left of column "column_num".  There is no "wraparound" in this world.  Thus it would be "illegal" to move left from column 0 or to move right from column 2.


Here is a state space diagram going from initial state:

A
B
C

 to goal state:

C	B	A

• Now draw the state space diagram for a FORWARD CHAINING (initial-to-goal) search.  Label each (directed) edge with the exact operator used to make the state transition.  Include duplicate states, but do not expand them (i.e., assume the search algorithm detects duplicate states):  (good idea:  draw each state with a TINY figure!)

• Now draw the state space diagram for a BACKWARD CHAINING (goal to initial) search:

For this problem, which is faster?  Forward or backward chaining?  Why?