A Controlled Expeniment on the Impact of Software Structure on Maintainability

This paper describes a study on the impact of software structure on maintainability aspects such as comprehensibility, locality, modifiability, and reusability in a distributed system environment. The study was part of a project at the University of Kaiserslautern, West Germany, to design and implement LADY, a LAnguage for Distributed systems. The study addressed the impact of software structure from two perspectives. The language designer´s perspective was to evaluate the general impact of the set of structural concepts chosen for LADY on the maintainability of software systems implemented in LADY. The language user´s perspective was to derive structural criteria (metrics), measurable from LADY systems, that allow the explanation or prediction of the software maintenance behavior. A controlled maintenance experiment was conducted involving twelve medium-size distributed software systems; six of these systems were implemented in LADY, the other six systems in an extended version of sequential Pascal. The benefits of the structural LADY concepts were judged based on a comparison of the average maintenance behavior of the LADY systems and the Pascal systems; the maintenance metrics were derived by analyzing the interdependence between structure and maintenance behavior of each individual LADY system.