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Key class identification approaches aim at identifying the most important classes to help developers, especially newcomers, start the software comprehension process. So far, many supervised and unsupervised approaches have been proposed; however, they have not considered the effort to comprehend classes. In this article, we identify the challenge of "effort-aware key class identification"; to partially tackle it, we propose an approach, EASE, which is implemented through a modification to existing unsupervised key class identification approaches to take into consideration the effort to comprehend classes. First, EASE chooses a set of network metrics that has a wide range of applications in the existing unsupervised approaches and also possesses good discriminatory power. Second, EASE normalizes the network metric values of classes to quantify the probability of any class to be a key class and utilizes Cognitive Complexity to estimate the effort required to comprehend classes. Third, EASE proposes a metric, RKCP, to measure the relative key-class proneness of classes and further uses it to sort classes in descending order. Finally, an effort threshold is utilized, and the top-ranked classes within the threshold are identified as the cost-effective key classes. Empirical results on a set of 18 software systems show that (i) the proposed effort-aware variants perform significantly better in almost all (≈98.33%) the cases, (ii) they are superior to most of the baseline approaches with only several exceptions, and (iii) they are scalable to large-scale software systems. Based on these findings, we suggest that (i) we should resort to effort-aware key class identification techniques in budget-limited scenarios; and (ii) when using different techniques, we should carefully choose the weighting mechanism to obtain the best performance. [ABSTRACT FROM AUTHOR]

Complex network theory has been successfully introduced into the field of software engineering. Many works in the literature have built complex networks in software, usually called software networks, to represent software structure. Such software networks and their related graph algorithms have been proved effective in predicting software bugs. However, the software networks used were unweighted and undirected, neglecting the strength and direction of the couplings. Worse still, they ignored many important types of couplings between classes, such as local variable, instantiates, and access. All of these greatly affect the accuracy of the software network in representing the topological detail of software projects and ultimately affect the metrics derived from it. In this work, an improved effort-aware bug prediction approach named CoreBug is proposed. First, CoreBug uses a weighted directed class dependency network (WDCDN) to precisely describe classes and their couplings, including nine coupling types and their different coupling strengths and directions. Second, a generalized k-core decomposition is introduced to compute the coreness of each class in the WDCDN. Third, CoreBug combines the coreness of each class with its relative risk, as returned by the logistic regression, to quantify the risk of a given class being buggy. Empirical results on eighteen Java projects show that CoreBug is superior to the state-of-the-art approaches according to the average ranking of the Friedman test. [ABSTRACT FROM AUTHOR]

Software maintenance is indispensable in the software development process. Developers need to spend a lot of time and energy to understand the software when maintaining the software, which increases the difficulty of software maintenance. It is a feasible method to understand the software through the key classes of the software. Identifying the key classes of the software can help developers understand the software more quickly. Existing techniques on key class identification mainly use static analysis techniques to extract software structure information. Such structure information may contain redundant relationships that may not exist when the software runs and ignores the actual interaction times between classes. In this paper, we propose an approach based on dynamic analysis and entropy-based metrics to identify key classes in the Java GUI software system, called KEADA (identifying KEy clAsses based on Dynamic Analysis and entropy-based metrics). First, KEADA extracts software structure information by recording the calling relationship between classes during the software running process; such structure information takes into account the actual interaction of classes. Second, KEADA represents the structure information as a weighted directed network and further calculates the importance of each node using an entropy-based metric OSE (One-order Structural Entropy). Third, KEADA ranks classes in descending order according to their OSE values and selects a small number of classes as the key class candidates. In order to verify the effectiveness of our approach, we conducted experiments on three Java GUI software systems and compared them with seven state-of-the-art approaches. We used the Friedman test to evaluate all approaches, and the results demonstrate that our approach performs best in all software systems. [ABSTRACT FROM AUTHOR]

Software stability means the resistance to the amplification of changes in software. It has become one of the most important attributes that affect maintenance cost. To control the maintenance cost, many approaches have been proposed to measure software stability. However, it is still a very difficult task to evaluate the software stability especially when software becomes very large and complex. In this paper, we propose to characterize software stability via change propagation simulation. First, we propose a class coupling network (CCN) to model software structure at the class level. Then, we analyze the change propagation process in the CCN by using a simulation way, and by doing so, we develop a novel metric, SS (software stability), to measure software stability. Our SS metric is validated theoretically using the widely accepted Weyuker's properties and empirically using a set of open source Java software systems. The theoretical results show that our SS metric satisfies most of Weyuker's properties with only two exceptions, and the empirical results show that our metric is an effective indicator for software quality improvement and class importance. Empirical results also show that our approach has the ability to be applied to large software systems. [ABSTRACT FROM AUTHOR]