How We Design Interfaces, and How to Assess It

Abstract

Abstract-Interfaces are widely used in Java applications as central design elements for modular programming to increase program reusability and to ease maintainability of software systems. Despite the importance of interfaces and a considerable research effort that has investigated code quality and concrete classes' design, few works have investigated interfaces' design. In this paper, we empirically study interfaces' design and its impact on the design quality of implementing classes (i.e., class cohesion) analyzing twelve Java object-oriented applications. In this study we propose the "Interface-Implementations Model" that we use to adapt class cohesion metrics to assess the cohesion of interfaces based on their implementations. Moreover, we use other metrics that evaluate the conformance of interfaces to the well-known design principles "Program to an Interface, not an implementation" and "Interface Segregation Principle". The results show that software developers abide well by the interface design principles cited above, but they neglect the cohesion property. The results also show that such design practices of interfaces lead to a degraded cohesion of implementing classes, where these latter would be characterized by a worse cohesion than other classes.

Refactoring Fat Interfaces Using a Genetic Algorithm

“…These results, together with Martin's insights [1] and results of previous studies [3], [4], motivated us to investigate and develop an approach to refactor fat APIs using the ISP.…”

“…In 2013, Abdeen et al [3] investigated empirically the impact of interfaces' quality on the quality of implementing classes. Their results show that violations of the ISP lead to degraded cohesion of the classes that implement fat interfaces.…”

“…First, in our previous work [2] we showed that such interfaces are more change-prone than nonfat interfaces. Next, Abdeen et al [3] proved that violations of the ISP lead to degraded cohesion of the components coupled to fat interfaces. Finally, Yamashita et al [4] showed that changes to fat interfaces result in a larger ripple effect.…”

“…We measure the compliance with the ISP of an interface through the Interface Cohesion Metric (IUC) as in [2], [3]. To apply the ISP we propose a multiobjective genetic algorithm that, based on the clients' usage of a fat interface, infers the interfaces into which it should be split to conform to the ISP and, hence, with higher IUC values.…”

Mining Multi-level API Usage Patterns

“…To measure the cohesion of usage patterns, we use the Service Usage Cohesion Metric (SIUC), taken from Perepletchikov et al [17]. SIUC was recently used in [18] to measure the usage cohesion of interfaces in Java OO applications, where, like our definition of a usage pattern, an interface is defined as a group of method An API providing a graphical user interface (GUI) for Java programs AWT An API for providing a platform dependent graphical user interface (GUI) for a Java program …”