showing that a program p has some property is a simple process if the actions inside the program are uninterruptible. however, when the action is interruptible, lipton showed that through a type of reduction and analysis, it can be shown that the reduced program has that property if and only if the original program has the property. if the reduction is done by treating interruptible operations as one large uninterruptible action, even with these relaxed conditions properties can be proven for a program p. thus, correctness proofs of a parallel system can often be greatly simplified.