Operators are composed of four parts: the goal type, the preconditions, the body and the shortcut condition. The goal type specifies the context for appropriate application of the operator. The preconditions enumerate the predicates that must hold for the operator to be valid. The body describes what will happen when the operator is executed including the new goals it will create. The shortcut condition is a flag that denotes, when true, that execution of the operator can be assumed to be completed.
There are three types of selection rules: consideration rules, rejection rules and preference rules. Consideration rules indicate that goals or operators apply to the current state. Rejection rules eliminate operators or goals from consideration. Preference rules provide a partial ordering of the goals or operators. The consideration rules are fired first, followed by the rejection rules and finally the preference rules. This is the state at which the agent will attempt to decide what to do.