A Qualitative Study on the Implementation Design Decisions of Developers

Decision-making is a key software engineering skill. Developers constantly make choices throughout the software development process, from requirements to implementation. While prior work has studied developer decision-making, the choices made while choosing what solution to write in code remain understudied. In this mixed-methods study, we examine the phenomenon where developers select one specific way to implement a behavior in code, given many potential alternatives. We call these decisions implementation design decisions. Our mixed-methods study includes 46 survey responses and 14 semistructured interviews with professional developers about their decision types, considerations, processes, and expertise for implementation design decisions. We find that implementation design decisions, rather than being a natural outcome from higher levels of design, require constant monitoring of higher level design choices, such as requirements and architecture. We also show that developers have a consistent general structure to their implementation decision-making process, but no single process is exactly the same. We discuss the implications of our findings on research, education, and practice, including insights on teaching developers how to make implementation design decisions. Index Terms-implementation design decisions, software design Implementation Architecture Requirements Consideration: What third-party libraries can I take dependencies on? ! Decision: How should I represent my matrix data- Python arrays, C++ arrays, or third-party libraries? Action: Prioritizing testability as a requirement after learning third-party libraries are hard to unit test while prototyping. Consideration: How important is memory for my use case? Action: Researching what similar modules or classes already use in their implementations. Class/Module