Relational programming laws in the tree, list, bag, set hierarchy

In this paper we demonstrate that the basic rules and calculational techniques used in two extensively documented program derivation methods can be expressed, and, indeed, can be generalized within a relational theory of datatypes. The two methods to which we refer are the so-called "Bird-Meertens formalism" for the construction of functional programs and the "Dijkstra-Feijen calculus" for the construction of imperative programs