Reening Speciications to Logic Programs

The reenement calculus provides a framework for the stepwise development of imperative programs from speciications. In this paper we study a reenement calculus for deriving logic programs. Dealing with logic programs rather than imperative programs has the dual advantages that, due to the expressive power of logic programs, the nal program is closer to the original speciication, and each reenement step can achieve more. Together these reduce the overall number of derivation steps. We present a logic programming language extended with speciication constructs (including general predicates, assertions, and types and invariants) to form a wide-spectrum language. General predicates allow non-executable properties to be included in speciications. Assertions, types and invariants make assumptions about the intended inputs of a procedure explicit, and can be used during reenement to optimize the constructed logic program. We provide a semantics for the extended logic programming language and derive a set of reenement laws. Finally we apply these to an example derivation.