Modeling Goals and Functions of Control and Safety Systems - theoretical foundations and extensions of MFM

Multilevel Flow Modeling (MFM) has proven to be an effective modeling tool for reasoning about plant failure and control strategies and is currently exploited for operator support in diagnosis [3, 4] and on-line alarm analysis [6]. Previous MFM research was focussed on representing goals and functions of process plants which generate, transform and distribute mass and energy [10, 11]. However, only a limited consideration has been given to the problems of modeling the control systems. Control functions are indispensable for operating any industrial plant. But modeling of control system functions has proven to be a more challenging problem than modeling functions of energy and mass processes. The problems were discussed by Lind [8, 9, 10] and tentative solutions has been proposed but have not been investigated in depth until recently, partly due to the lack of an appropriate theoretical foundation. The purposes of the present report are to show that such a theoretical foundation for modeling goals and functions of control systems can be built from concepts and theories of action developed by Von Wright [23] and to show how the theoretical foundation can be used to extend MFM with concepts for modeling control systems. The theoretical foundations has been presented in detail elsewhere by the present author [12, 14] without the particular focus on modeling control actions and MFM adopted here.