Guidelines for automated implementation of executable object oriented models for real-time embedded control systems

We present our experiences in applying real time scheduling theory to embedded control systems designed using ROOM (Real time Object Oriented Modeling) methodology. ROOM has originated from the telecommunications community and has been successfully applied to many commercial systems through the supporting case tool ObjecTime. It is particularly suitable for modeling reactive real time behavior. Furthermore, it provides many other advantages through the use of object orientation, and the use of executable models from which code may be generated quickly and efficiently. Since many real time embedded control systems have significant reactive, event driven behavior, it is attractive to use ROOM methodology to develop such systems. However, the ROOM methodology does not provide tools to specify and analyze the temporal behavior as is required for the hard real time components of embedded systems, and for which the real time scheduling theory provides an analytical basis. We show how real time scheduling theory may be applied to ROOM models using a cruise control example to illustrate. The biggest challenge comes from minimizing the adverse effects of priority inversions. Our results are very encouraging, and we show that not only is it possible to apply real time scheduling theory, but that it can be done very efficiently provided certain guidelines are followed in the design and implementation of the ROOM model.