purcell%loki.edsg@HAC2ARPA.HAC.COM (ed purcell) (11/19/88)
Some observations on the request of quintus!ok@unix.sri.com (16 Nov 88) for references on the term ``iterative deepening'': In his IJCAI85 paper on the IDA* (Iterative Deepening A*) search algorithm for state-space problem graphs, Rich Korf of UCLA acknowledges early chess-playing programs as the first implementations of the idea of progressively deeper searches. (The history of progressively deeper look-ahead searches for game trees is somewhat reminiscent of the history of alpha-beta pruning -- these clever algorithms were both implemented early but not immediately published nor analyzed until many years later.) The closely-related term ``progressive deepening'' also has been around awhile; for example, this term is used in the 2nd edition (1984) of Pat Winston's textbook ``An Introduction to AI.'' The contributions of Korf's IJCAI85 paper on IDA* are in the re-formulation and analysis of progressively deeper depth-first search for state-space graphs, using a heuristic evaluation function instead of a fixed depth bound to limit node expansions. It is interesting that Korf is now investigating the re-formulation of minimax/alpha-beta pruning for state-space graphs. Ed Purcell purcell%loki.edsg@hac2arpa.hac.com 213-607-0793