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UBC Theses and Dissertations

Understanding motifs of program behaviour and change Alimadadi Jani, Saba


Program comprehension is crucial in software engineering; a necessary step for performing many tasks. However, the implicit and intricate relations between program entities hinder comprehension of program behaviour and change. It is particularly a difficult endeavour to understand dynamic and modern programming languages such as JavaScript, which has grown to be among the most popular languages. Comprehending such applications is challenging due to the temporal and implicit relations of asynchronous, DOM-related and event-driven entities spread over the client and server sides. The goal of the work presented in this dissertation is to facilitate program comprehension through the following techniques. First, we propose a generic technique for capturing low-level event-based interactions in a web application and mapping those to a higher-level behavioural model. This model is then transformed into an interactive visualization, representing episodes of execution through different semantic levels of granularity. Then, we present a DOM-sensitive hybrid change impact analysis technique for JavaScript through a combination of static and dynamic analysis. Our approach incorporates a novel ranking algorithm for indicating the importance of each entity in the impact set. Next, we introduce a method for capturing a behavioural model of full-stack JavaScript applications’ execution. The model is temporal and context-sensitive to accommodate asynchronous events, as well as the scheduling and execution of lifelines of callbacks. We present a visualization of the model to facilitate program comprehension for developers. Finally, we propose an approach for facilitating comprehension by creating an abstract model of software behaviour. The model encompasses hierarchies of recurring and application-specific motifs. The motifs are abstract patterns extracted from traces through our novel technique, inspired by bioinformatics algorithms. The motifs provide an overview of the behaviour at a high level, while encapsulating semantically related sequences in execution. We design a visualization that allows developers to observe and interact with inferred motifs. We implement our techniques in open-source tools and evaluate them through a set of controlled experiments. The results show that our techniques significantly improve developers’ performance in comprehending the behaviour and impact of change in software systems.

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