Source code comprehension strategies and metrics to predict comprehension effort in software maintenance and evolution tasks - an empirical study with industry practitioners

The goal of this research was to assess the consistency of source code comprehension strategies and comprehension effort estimation metrics, such as LOC, across different types of modification tasks in software maintenance and evolution. We conducted an empirical study with software development practitioners using source code from a small paint application written in Java, along with four semantics-preserving modification tasks (refactoring, defect correction) and four semantics-modifying modification tasks (enhancive and modification). Each task has a change specification and corresponding source code patch. The subjects were asked to comprehend the original source code and then judge whether each patch meets the corresponding change specification in the modification task. The subjects recorded the time to comprehend and described the comprehension strategies used and their reason for the patch judgments. The 24 subjects used similar comprehension strategies. The results show that the comprehension strategies and effort estimation metrics are not consistent across different types of modification tasks. The recorded descriptions indicate the subjects scanned through the original source code and the patches when trying to comprehend patches in the semantics-modifying tasks while the subjects only read the source code of the patches in semantics-preserving tasks. An important metric for estimating comprehension efforts of the semantics-modifying tasks is the Code Clone Subtracted from LOC(CCSLOC), while that of semantics-preserving tasks is the number of referred variables.