n Numerical Example (b=10, l = 5) n Bi-directional search finds solution at d=3 for both forward and backward search.  Assuming BFS in each half 2222 nodes are expanded. n Implementation issues: n Operators are reversible, e.g., Pred(Succ(n)) = Pred(Succ(n)) n There may be many possible goal states. n Construct a goal state containing the superset of all goal states. n Check if a node appears in the “other” search tree. n Using different search strategies for each half.