Search Methods Using Heuristic Strategies

As the metalevel problem M is no d i f f e r e n t from any other problem, the basic procedure outl i ned above, or some v a r i a t i o n of i t , can be used to generate a so l u t i on to M, and hence to P. However, in almost a l l cases we can expect the metal e v e l problem to be commutative — tha t i s , i f f o r a given s ta te there ex i s t s a number of possib le successors, and one of these leads to a s o l u t i o n , then so do a l l the o thers . In such a s i t u a t i o n there is no need to back-up and consider previous s ta tes of the computation. In systems tha t are r e ­ quired to I n t e rac t w i t h exper ts , such un i f o rm i t y o f knowledge representa t ion is an important consider­ a t i o n . Furthermore, w i t h such a scheme i t is poss­ i b l e to provide a h ierarchy of metalevel problems and s t r a t e g i e s , each determining how to handle the non-determinism of the one below i t .