Abstract
Context. Coupling between classes is an important metric for software complexity in software systems. Objective. In order to overcome the shortcomings of the existing coupling methods and fully investigate the weighted coupling of classes in different cases in large-scale software systems, this study analyzed the relationship between classes at package level, class level, and method level. Method. The software system is considered as a set of special bipartite graphs in complex networks, and an effective method for coupling measurement is proposed as well. Furthermore, this method is theoretically proved to satisfy the mathematical properties of coupling measurement, leading to overcome the disadvantages of the majority of existing methods. In addition, it was revealed that the proposed method was efficient according to the analyses of existing methods for coupling measurement. Eventually, an algorithm was designed and a program was developed to calculate coupling between classes in three open-source software systems. Results. The results indicated the scale-free characteristic of complex networks in the statistical data. Additionally, the calculated power-law value was used as a metric for coupling measurement, so as to calculate coupling of the three open-source software. It indicated that coupling degrees of the open-source software systems contained a certain impact on evaluation of software complexity. Conclusions. It indicated that coupling degrees of the open-source software systems contained a certain impact on evaluation of software complexity. Moreover, statistical characteristics of some complex networks provided a reliable reference for further in-depth study of coupling. The empirical evidence showed that within a certain range, reducing the coupling was helpful to attenuate the complexity of the software, while excessively blindly pursuit of low coupling increases the complexity of software systems.
Highlights
Coupling refers to the degree of interdependence between software modules; a measure of how closely connected two routines or modules are [1]; and the strength of the relationships between modules
Based on bipartite graphs for complex networks, by comprehensive consideration of the weighted fan-out between classes from points of view of package level, class level, and method level, this study expressed that the interaction of classes is a special bipartite graph, while a software system is a set of these special bipartite graphs
Coupling relationship for classes in a package with other classes in different layers of the package was taken into account. erefore, the CSBG method for coupling measurement of software systems was proposed, which was completely in compliance with the mathematical characteristics of the widely accepted metrics
Summary
Coupling refers to the degree of interdependence between software modules; a measure of how closely connected two routines or modules are [1]; and the strength of the relationships between modules. Structured design, including cohesion and coupling, was published in an article by Stevens et al and a book by Stevens et al [2, 3], and the latter subsequently became standard terms. Object-oriented software development (OOSD) includes object-oriented requirement analysis, as well as object-oriented design. Interactions between objects reflect the interdependence between objects. The software system can only achieve simple functions. Objects are equivalent to cells in human body. If cells are completely isolated from human body, they basically do not play any significant role, reflecting that functions of a software system require a tight coupling between objects. Tight coupling between objects would lead to a water-wave effect, meaning that changes in one object may result in further changes in other objects. Tight coupling between objects would lead to a water-wave effect, meaning that changes in one object may result in further changes in other objects. e most terrible case is that there is a possibility of “avalanche” effect, which may affect the whole system, leading to a sharp decline in the testability, understandability, reliability, and maintainability
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