Componentwise Program Construction: The Equivalent Transformation Computation Model versus the Logic Programming Model

In the equivalent transformation (ET) computation model, a program is a set of procedural rewriting rules for answer-preserving transformation of problems with respect to given background knowledge. In this paper, we discuss an approach to program construction by creating and accumulating individually correct and efficient program components one by one, referred to as componentwise program construction. Basic requirements for componentwise program construction are identified, based on which we show that the ET model possesses several desirable properties for this program construction approach, in particular, compared with the logic programming model. In addition, we compare the expressive power of program components in the ET model and that of components in the logic programming model by viewing computation in the latter model as problem transformation using only one specific class of rewriting rules, i.e., single-head general unfolding-based rules, and then demonstrating that a larger class of rules is needed for effective computation. Key–Words: Componentwise program construction, Equivalent transformation, Rule-based computation, Program synthesis, Rewriting rules, Computation paradigm