Up to now we have assumed that actions are only executed in the appropriate situations.

Let us see what propositional successor-state axioms sixh as Equation (1 1.1) have to say about actions whose preconditions are not satisfied.

a. Show that the axioms predict that nothing will happen when an action is executed in a state where its preconditions are not satisifed.

b. Consider a plan p that contains the actions required to achieve a goal but also includes illegal actions. Is it the case that initial state A successov-state axioms A p /= goal ?

c. With first-order successor-state axioms in situation calculus (as in Chapter lo), is it possible to prove that a plan containing illegal actions will achieve the goal?