Structured Specifications and Implementation of Nondeterministic Data Types

The use of nondeterminism in speci cations as distinct from underspeci cation is moti vated by an example in the context of data re nement A simple formalism for specifying nondeterministic data types is introduced Its semantics is given in terms of the existing formalisms of relations multialgebras sets of functions and oracles by means of appropri ate translation rules Nondeterministic data re nement is studied from the syntactic and semantic perspective and the correctness of the suggested proof obligations is proved More general the implementation relation and parameterisation of nondeterministic data types are discussed and the standard theorems of vertical and horizontal composition are generalized to the nondeterministic case