PWORLD: A Precedent-Based Global Simulation.

A "world model" is constructed where precedent-searching is one of the primary driving mechanisms. The simulation assumes that nations in the system are utility maximizers but that they have relatively primitive decision mechanisms and that they are strongly influenced by their previous short-term successful behavior and the short-term success of other states in the system. This model of foreign policy decision-making has been heavily influenced by recent artificial intelligence studies and simulations. States in the simulation follow one of three distinct strategies to maximize growth: imperialism, militarism, or trade and, in each mode, a state can increase or decrease its level of behavior, or it can switch modes. The objective of simulation is to get away from the purely mechanistic difference equation formulations of world models while avoiding overly rational and optimizing models. Precedent-based decision-making is plausible for a goal-seeking system which, because of bureaucratic constraints, is capable of only fairly simple behaviors. The simulation uses a system vaguely characteristic of the 19th century world system with 5 large, 5 medium, and 10 small nations. The resulting behavior is generally plausible with bounded and fairly diverse activity depending on the random experimentation involved. Because of the weak bounded rationality, the system does not lock on to a single pattern of behavior based on initial conditions and so, for example, siutations exist where medium powers eventually become stronger than the initial major powers. The most common pattern is one of a combination of trade links and imperialism, with about half the minor powers being colonized and some exchange of colonies occurring through conflict. An appendix, "Key Elements of PWorld Program", and a bibliography are included. (Author/KWL)