UC Irvine

The principle of information hiding has been very influential in software engineering since its inception in 1972. This principle prescribes that software modules hide implementation details from other modules in order to reduce their dependencies. This separation also decreases the dependency among software developers implementing these modules, thus simplifying the required coordination. A common instantiation of this principle widely used in the industry is in the form of application programming interfaces (APIs). While previous studies report on the general use and benefits of APIs, they have glossed over the detailed ways in which APIs facilitate the coordination of work. In order to unveil these mechanisms, we performed a qualitative study on how practitioners use APIs in their daily work. Using ethnographic data from two different software development teams, we identified three roles played by APIs in the coordination of software development projects. These roles are described using three metaphors: APIs as contracts, APIs as boundaries, and APIs as communication mechanisms. As contracts, APIs allow software developers to work in parallel and independently. As a communication mechanism, APIs facilitate communication among software developers by giving them something specific to talk about. At the same time, APIs establish the boundaries between developers, and, accordingly, what should be talked about. This paper also reports on problems the studied teams face when using APIs to coordinate their work. Based on these results, we draw theoretical implications for collaborative software engineering.