In problem solving, the problem space is the set of all possible operations that can be performed in an attempt to reach a solution. The idea is credited, at least in one place, to A. Newell, who defined the problem space principle as “The rational activity in which people engage to solve a problem can be described in terms of (1) a set of states of knowledge, (2) operators for changing one state into another, (3) constraints on applying operators and (4) control knowledge for deciding which operator to apply next.”
