An observational study on API usage constraints and their documentation

Nowadays, APIs represent the most common reuse form when developing software. However, the reuse benefits depend greatly on the ability of client application developers to use correctly the APIs. In this paper, we present an observational study on the API usage constraints and their documentation. To conduct the study on a large number of APIs, we implemented and validated strategies to automatically detect four types of usage constraints in existing APIs. We observed that some of the constraint types are frequent and that for three types, they are not documented in general. Surprisingly, the absence of documentation is, in general, specific to the constraints and not due to the non documenting habits of developers.