Modeling Sequences within the RelView System

We use a relational characterization of binary direct sums to model sequences within the relation-algebraic manipulation and prototyping system RelView in a simple way. As an application we formally derive a RelView program for computing equivalence classes of an equivalence relation, where we combine relation-algebraic calculations with the so-called Dijkstra-Gries program development method. Also a refinement of the simple modeling is presented, which leads to the classical datatype of stacks, and a further application is sketched.