Issue No.10 - October (1969 vol.18)
N.J. Nilson , Stanford Research Institute
One of the prominent research topics in Artificial Intelligence continues to be the development of problem-solving methods in which the process of "search" plays a vital role. In the usual formulation,  one imagines a space of "objects" and a collection of "operators." The objects are data structures such as strings, lists, arrays, etc. that represent problem "states." The operators map objects into other objects. A problem to be solved is then translated into the task of finding a sequence of operators that will map an initial object into a goal object. Among the problems that have been formulated in this fashion are puzzles (the missionaries and cannibals problem, the Tower of Hanoi problem), problems in mathematics (symbolic integration, proving theorems in geometry), parsing sentences, proving theorems in the predicate calculus, and problems of commonsense reasoning about actions.
N.J. Nilson, "R69-31 A Formal Deductive Problem-Solving System", IEEE Transactions on Computers, vol.18, no. 10, pp. 963-964, October 1969, doi:10.1109/T-C.1969.222558