Evaluation and improvement of software architecture: identification of design problems in object-oriented systems and resolution through refactorings

Abstract

Maintenance has gained the most important role in the life cycle of a software product, since it occupies the largest percentage of software development costs. This can be attributed to the fact that a software product should constantly evolve by providing new features, error corrections, performance improvements, and integration of novel technologies in order to remain competitive and diachronically successful. Despite the major importance of software maintenance, the effort being invested by software companies on preventive maintenance (i.e., improvement of design quality in order to increase maintainability) is very limited (lower than 5% of total maintenance costs). This fact indicates that there is a clear need for methods and tools that can be used by the software industry in order to support preventive maintenance, since the manual and human-driven inspection of source code requires tremendous effort and leads to long-term benefits that do not add immediate value to the software product. To this end, this work aims at developing methods and techniques that provide a concrete solution for major design problems whose remedy improves design quality and facilitates increased maintainability. The developed methods face the problem of improving the design quality of an object-oriented system by means of identifying refactoring opportunities which resolve bad smells existing in source code. This refactoring-oriented approach has the ability to produce refactoring solutions which are feasible and behavior preserving by examining a set of preconditions that should apply, pre-evaluate the impact of the identified refactoring opportunities on certain aspects of design quality and provide a ranking of the refactoring solutions allowing the prioritization of maintenance effort on parts of the program that would benefit the most. Therefore, it can be claimed that this work provides the most adequate support for the refactoring process which constitutes a major part of preventive maintenance