A Template for Design Transform Specification

Migration from a procedural architecture to an objectoriented architecture is possible through an appropriate sequence of design transformations. This paper initially provides a conceptual foundation for migration from a procedural to an object-oriented software architecture for legacy software, which relies upon a view of the software life cycle, in which all software development is considered to be an evolutionary activity wherein reengineering/restructuring is an important process applied repeatedly on the artefacts of development at various stages in this evolution. We then introduce a novel approach of viewing a procedural program from an object-oriented perspective in which there is a single “god” class which has a large number of global variables and methods, supported by several userdefined classes which have no behaviour, only data definitions. This view, coupled with repeated restructuring, enables a seamless migration of behaviour from the god class to other classes using design transformation methods. There is a distinction between the processes of translation and transformation, processes that we contend are orthogonal to each other, which thereby enables us to concentrate on behaviourpreserving design transformations in order to migrate from one design to another, leaving the language issues to be handled by translators. Having established the need for behaviour-preserving design transformations, we provide a template for specifying design transformations. The main contribution of this paper is in the proposal of a template for the communication of design transformations. An example design transformation is presented which demonstrates the usefulness of the proposed template.