Refactoring with domain-driven design in an industrial context: An action research report

Abstract

Context: Software developers need to constantly work on evolving the structure and the stability of the code due to changing business needs of the product. There are various refactoring approaches in industry which promise improvements over source code composition and maintainability. Objective: In our research, we want to improve the maintainability of an existing system through refactoring using Domain-Driven Design (DDD) as a software design approach. We also aim for providing empirical evidence on its effect on maintainability and the challenges as perceived by developers. Method: In this study, we applied the action research methodology, which facilitates close academia-industry collaboration and regular presence in the studied product. We utilized focus groups to discover problems of the existing system with a qualitative approach. We reviewed the subject codebase to construct our own expert opinion as well and identified problems in the codebase and matched them with the ones raised by engineers in the team. We refactored the existing software system according to DDD principles. To measure the effects of our actions, we utilized Technology Acceptance Model (mTAM) questionnaire, and also semi-structured interviews with the development team for data collection, and card sorting methodology for qualitative analysis. For minimizing bias that might affect our results with the existing software engineers in the team, we extended our measurement with three new joiner software engineers in the team through the think aloud protocol. Results: We have identified that engineers mostly gave positive answers to our interview questions, which are mapped to software maintainability metrics defined by ISO/IEC 25010. Our DDD refactoring scored 85 in PU and 83 in PEU, leading to an overall mTAM score of 84. This means acceptable on the acceptability scale, B on the grade scale, and good on the adjective rating scale. Conclusion: Our research led us to conclude that a powerful design approach, like DDD, is an effective tool for restructuring and resolving software issues in this situation. It offers standardization to the software and the refactoring efforts. We realized that DDD entails a certain degree of complexity and cognitive load, which is a barrier for software engineers, but they are aware of its benefits.