Missionaries and Cannibals in the Causal Calculator

A knowledge representation formalism is \elaboration tolerant" to the extent that it is convenient to modify a set of facts expressed in the formalism to take into account new phenomena or changed circumstances. John McCarthy illustrated this idea by deening 19 elaborations of the Missionaries and Cannibals Problem. We argue that, to a certain degree, the goal of elaboration tolerance is met by the input language of Norman Mc-Cain's Causal Calculator. We present formal descriptions of the basic Missionaries and Cannibals Problem and of ten of McCarthy's enhancements as input les accepted by the Causal Calculator. Each enhancement is obtained from the basic formulation by the simplest kind of elaboration|adding postulates.