Active inference of EFSMs without reset

Extended finite state machines (EFSMs) model stateful systems with internal data variables, and have many software engineering applications, including system analysis and test case generation. Where such models are not available, it is desirable to reverse engineer them by observing system behaviour, but existing approaches are either limited to classical FSM models with no internal data state, or implicitly require the ability to reset the system under inference, which may not always be possible. In this paper, we present an extension to the hW-inference algorithm that can infer EFSM models, complete with guards and internal data update functions, from systems without a reliable reset, although there are currently some restrictions on the type of system and model.