Constraint Satisfaction

1
Constraint Satisfaction
2
Agenda

• Constraint Satisfaction Overview
• Thagard, 1989
• Golstone Rogosky, 2002

3
Constraint Satisfaction

• The goal is to discover a solution to a problem
  that satisfies a set of constraints that are not
  intrinsic to the problem in general.

4
Constraint Satisfaction

• The main benefit of viewing a problem as one of
  constraint satisfaction is computational.
• In particular, less search is required.

5
Cryptarithemetic Problem

• SEND
• MORE
• ------------
• MONEY

Rich Knight, 1991 Example
6
Cryptarithemetic Problem

• SEND MORE MONEY
• Goal To map letters to numbers in such a way
  that the initial constraints are satisfied.

7
Cryptarithemetic Problem
M 1 S 8 or 9 O 0 or 1 ?O 0 N E or E 1
? N E 1 C2 1 NR gt 8 E ?9
SEND MORE ----------- MONEY
E2
N 3 R 8 or 9 2 D Y or 2 D 10 Y
C10
C11
2 D 10 Y D 8 Y D 8 or 9
2 D Y N R 10 E R 9 S 8
D 8
D 9
X
X
Y 1
Y 0