A continuous ASM modelling approach to pacemaker sensing

The cardiac pacemaker system, proposed as a problem topic in the Verification Grand Challenge, offers a range of difficulties to address for formal specification, development, and verification technologies. We focus on the sensing problem, the question of whether the heart has produced a spontaneous heartbeat or not. This question is plagued by uncertainties arising from the often unpredictable environment that a real pacemaker finds itself in. We develop a time domain tracking approach to this problem, as a complement to the usual frequency domain approach most frequently used. We develop our case study in the continuous ASM (Abstract State Machine) formalism, which is briefly summarised, through a series of refinement and retrenchment steps, each adding new levels of complexity to the model.