EASE: An Effort-aware Extension of Unsupervised Key Class Identification Approaches

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.