Protocol Programmability

Application Programming Interfaces (APIs) often define protocols— restrictions on the order of client calls to API methods. API protocols are common and difficult to follow, which has generated tremendous research into the specification and verification of protocols. However, verification techniques do little to alleviate several major challenges programmers face when using API protocols: fixing protocol violations, learning protocol rules, and finding state transitions. To understand these challenges better, I mined developer forums to identify problems that developers have with protocols. Then, I performed a think-aloud observational study, in which I systematically observed profes-sional programmers struggle with these same problems to get more detail on the nature of their struggles and how they used available resources. In my observations, programmer time was spent primarily on four types of searches of the protocol state space