Another Constraint Satisfaction Example

Federal Express needs to deliver four packages a,b,c, and d at one of four times, 1,2,3, or 4. Let A represent the time at which a is delivered, B represent the time at which b is delivered, etc. The initial possible values for each delivery is the set {1, 2, 3, 4}. The following constraints need to be met:

(B &ne 3) ^ (C &ne 2) ^ (A &ne B) ^ (B &ne C) ^ (C < D) ^ (A = D)^ (B &ne D)

If you applied backtracking search to this, how would the search tree develop (consider the variables/values in sorted order).

How would using the following change the search?

  • Most constrained variable
  • Most constraining variable
  • Least constraining value
  • Forward-checking search