1. A system for specifying an expert system, comprising: circuitry for generating a plurality of task specifications for specifying tasks as functional units of the expert system; circuitry for generating a plurality of method specifications for specifying a plurality of methods identifying a plurality of ways for accomplishing ones of said tasks; circuitry for specifying at least one said task as a subtask of a selected one of said methods, such that ones of said task specifications are organized as a structure having multiple levels of said tasks; circuitry for generating at least one task level task state expression specifying an interaction between a first one of said tasks at a first level of said structure and a second one of said tasks at said second level of said structure; circuitry for generating at least one method level task state expression specifying a control flow between each said subtask of said selected one of said methods, wherein one of said first and second tasks is a particular subtask of a particular one of said methods; combining circuitry for combining said task level task state expression with said method level task state expression to establish a combined task state expression; and verifying circuitry for verifying whether said particular subtask is consistent with said particular method in response to said combined task state expressions.