Mapping the Space of API Design Decisions

When creating new application programming interfaces (APIs), designers must make many decisions. These decisions affect the quality of the resulting APIs in terms of performance (such as speed and memory usage), power (expressiveness, extensibility and evolvability) and usability (learnability, productivity and error prevention). Experienced API designers have written recommendations on how to design APIs, offering their opinions on various API design decisions. Additionally, empirical research has begun to measure the usability tradeoffs of specific design decisions. While previous work has offered specific suggestions, there has not been a clear description of the design space of all possible API design decisions, or the quality attributes that these decisions affect. This paper puts existing API design recommendations into context by mapping out the space of API design decisions and API quality attributes.