Decomposing Legacy Programs: A First Step Towards Migrating to Client-Server Platforms

A solution to the problem of salvaging the past investments in centralised, mainframe-oriented software development, while keeping competitive in the dynamic business world, consists of migrating legacy systems towards more modern environments, in particular client–server platforms. However, a migration process entails costs and risks that depend on the characteristics of both the architecture of the source system and the target client–server platform. We propose an approach to program decomposition as a preliminary step for the migration of legacy systems. A program slicing algorithm is defined to identify the statements implementing the user interface component. An interactive re-engineering tool is also presented that supports the software engineer in the comprehension of the source code during the decomposition of a program. The focus of this paper is on the partition of a legacy system, while issues related to the re-engineering, encapsulation, and wrapping of the legacy components and to the definition of the middleware layer through which they communicate are not tackled