Nondeterminism vs. Underspecification

The paper illustrates how nondeterministic operators supply a useful, and even necessary , abstraction mechanism, and how the common alternative, underspecification is insufficient even in quite simple examples. We show how underspecification actually forces one to overspecify by requiring additional assumptions not implied by the statement of the problem to be described. We indicate the tight relation between inherently unordered data types, like sets, and the nondeterminisitc (choice) operations which provide natural and adequate means for iteration over such data types