Towards intelligibility in sensor programming

Sensors and sensor-rich embedded systems are eminently applicable for autonomous monitoring and control in noncommercial, home or professional environments, besides their increasing use in medical and ecological settings, or mainstream use in industrial control. Having end users realize, deploy and interact with sensor-based embedded systems is conditioned, among others, by the availability of tools and techniques for end-user software engineering [8] specialized for these embedded systems. At their application logic, embedded sensor applications are inherently context aware: they most often implement context awareness by a deterministic stateand rule-based decision logic to trigger an output actuation out of a set of inputs from the environment. The logic can thus be seen as a finite-state machine, with rules transitioning between states, given an input from the environment. Since in embedded sensor systems this stateand rule-based decision model is distributed (i.e. a particular sensor node triggers an output with taking input from neighbour nodes) this gives that an application’s input set may be large, and the decision model complex. On the other hand, embedded sensors are limited in computational resources. Thus, the programming of these applications is done close to the hardware; microcontroller programmers avoid higher-level languages altogether, as C is perceived as an inherently efficient language due to it being low-level. This efficiency, however, limits expressivity and consequently intelligibility of the application. This last fact also explains why embedded software engineering is still in the domain of professional programmers; research on enduser embedded software engineering is yet to fully develop. In the long term, of interest are “[analysis] tools for enduser programmers which are integrated with the users’ [software development] and are incremental in their feedback”[8]. Such tools may, e.g., automatize the task of collecting relevant information about the program logic from program source, for the purpose of program maintenance (such as