Several search trees have been introduced
above. In each tree one of the paths from the
root node to a leaf node represents the optimal
solution. The task of the tree search method is
to systematically scan the search tree for this best
solution. The common tree search methods which
can be found in most textbooks on artificial intelligence
(Barr and Feigenbaum, 1981; Nilsson, 1982;
Pearl, 1984), differ in the order in which they scan
the branches of the search tree. Since search trees
tend to be very large, heuristic search strategies are
used in addition to the standard search methods in
order to reduce the average search times