Unveiling the usability of reactive programming APIs: findings, tools, and recommendations

Abstract

Reactive Programming (RP) has gained traction for its ability to simplify the development of event-driven and asynchronous applications. Despite its growing popularity, the usability of application programming interfaces (APIs) of RP remains a significant challenge for developers, with issues ranging from steep learning curves to inconsistent design practices (e.g., divergent number of operators and interfaces). This thesis explores the usability of RP APIs through a combination of approaches: mining studies, metrics, and user-centered evaluations. The first part of the study leverages data from GitHub and Stack Overflow to analyze how developers

interact with RP APIs, identifying operators’ frequency (a common design problem) and re- curring pain points. The second part employs a mixed-method approach, combining structural,

computed metrics with qualitative user study to assess API usability, employing a refined Cog- nitive Dimensions framework (CDN). Metrics are computed using our implemented tool, UAX

(Usability Analyzer Experience), which embodies a set of six metrics explored in other studies. The user-centered evaluation further examines aspects like understandability, learnability, and expressiveness through task-based experiments and user feedback. Results highlight significant disparities between API design and usability, providing a clearer understanding of the real-world challenges users encounter. The thesis culminates in a set of practical recommendations for the designers, aimed at enhancing RP API usability and aligning it with users’ needs. Contributions include a comprehensive usability analysis of RP APIs, empirical findings from the open-source community, answers for recurrent problems (i.e., excessive number of operators), the UAX tool, the first appliance of a user-centered evaluation with CDN and RP, recommendations for API improvements, and a foundation for future RP usability researches. This work lays the groundwork for enhancing the developer experience in RP interfaces and contributes to the broader field of software engineering.