Goals, Operators, Methods and Selection Rules (P. Johnson)
Goals: Symbolic structure that define a state of affairs to be achieved and determine a set of possible methods by which it may be accomplished.
Operators: theses are elementary perceptual, motor or cognitive acts whose execution is necessary to change any aspects of the users mental state or to affect the task environment
Methods: methods are descriptions of procedures for achieving goals. They are conditional sequences of goals and operators.
Selection Rules: There are may be more than one method for achieving a give goal. The selection rules handle the process of choosing between methods, in the form of ‘ IF X THAN M’.