Abstract
Class cohesion is an important quality attribute that has an impact on other quality attributes such understandability, testability, and maintainability. Therefore, classes with low cohesion should be refactored in order to improve their overall qualities. Many cohesion metrics have been introduced in the literature to automatically assess the quality of the class and support refactoring activities. Most existing metrics measure the class cohesion based on how the methods of a class are internally related to each other, while a few metrics measure the class cohesion based on how the methods are externally used by the clients of the class. Unfortunately, the existing client-based cohesion metrics cannot automatically support refactoring techniques such as the Extract Class refactoring. Therefore, this article proposes a new client-based cohesion metric that can be used to automatically identify Extract Class refactoring opportunities. The proposed metric is theoretically evaluated by proving the compliance of the metric to the mathematical cohesion properties, while it is empirically evaluated by conducting a large case study on three systems to compare the metric with other cohesion metrics. Finally, the paper introduces and evaluates an Extract Class refactoring approach based the proposed cohesion metric.
Highlights
S OFTWARE developers strive hard to design classes with high quality
We refer to this kind of similarity as client similarity between methods and we call the proposed metric COHESION BASED ON CLIENT SIMILARITY BETWEEN METHODS (CCSM) which stands for Cohesion based on Client Similarity between Methods
Our results indicate that CCSM is potentially useful and may offer benefits not offered by the other metrics
Summary
S OFTWARE developers strive hard to design classes with high quality. Class cohesion is one of the most important quality attributes that influences the maintainability of the class [1], [2]. Most of existing class cohesion metrics (e.g, [6]–[10] ) fall into the first category in which class cohesion is measured based on information extracted from the internal elements (methods and attributes) of the class regardless the other classes in the system. The new metric measures the cohesion of a class based on the similarities (in terms of clients’ usage) between each pair of methods including the non-public methods. We refer to this kind of similarity as client similarity between methods and we call the proposed metric CCSM which stands for Cohesion based on Client Similarity between Methods.
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