Concept Analysis for Module Restructuring

Low coupling between modules and high cohesion inside each module are the key features of good software design. This paper proposes a new approach to using concept analysis for module restructuring, based on the computation of extended concept subpartitions. Alternative modularizations, characterized by high cohesion around the internal structures that are being manipulated, can be determined by such a method. To assess the quality of the restructured modules, the trade-off between encapsulation violations and decomposition is considered, and proper measures for both factors are defined. Furthermore, the cost of restructuring is evaluated through a measure of distance between the original and the new modularizations. Concept subpartitions were determined for a test suite of 20 programs of variable size: 10 public-domain and 10 industrial applications. The trade-off between encapsulation and decomposition was measured on the resulting module candidates, together with an estimate of the cost of restructuring. Moreover, the ability of concept analysis to determine meaningful modularizations was assessed in two ways. First, programs without encapsulation violations were used as oracles, assuming the absence of violations as an indicator of careful decomposition. Second, the suggested restructuring interventions were actually implemented in some case studies to evaluate the feasibility of restructuring and to deeply investigate the code organization before and after the intervention. Concept analysis was experienced to be a powerful tool supporting module restructuring.