Sometimes you need to see through walls - A field study of application programming interfaces

Information hiding is one of the most important and influential principles in software engineering. It prescribes that software modules hide implementation details from other modules in order to decrease the dependency between them. This separation also decreases the dependency among software developers implementing modules, thus simplifying some aspects of collaboration. A common instantiation of this principle is in the form of application programming interfaces (APIs). We performed a field study of the use of APIs and observed that they served many roles. We observed that APIs were successful indeed in supporting collaboration by serving as contracts among stakeholders as well as by reifying organizational boundaries. However, the separation that they accomplished also hindered other forms of collaboration, particularly among members of different teams. Therefore, we argue that APIs do not only have beneficial purposes. Based on our results, we discuss implications for collaborative software development tools. Copyright 2004 ACM.