A Process Algebra for Predictible Control Systems

Published in Volume XI, 2002, p. 231-245

Author(s): Nicolae MARIAN

Abstract

This paper presents Process Algebra for Predictible Control Systems (PAPCS) as a model for specifying and analysis of concurrent, time and resource dependent, distributed control systems. Instantaneos, prioritized events are used for process synchronization, more or less as in other existing process algebra approaches. Events with bound delays are used for interprocess communication. The building blocks of PAPCS are processes, consisting of activities, by their turn combining resource, priority, and time consuming composite functions. Activities can generate specific reactions to timing and/or events. They can also include variables in a C like statement. Because of introducing prioritized resources and events, our algebra allows activities or events to take priority over others and therefore to capture a notion of preemption. Fixed-priority scheduling of execution and communication is used in order to assure safe and preditable behaviour, in the context of local and remote interactions. Timing analysis techniques can be carried out. Operators like interrupt and timeout are integrated in PAPCS. Using the notion of bisimulation as a basis, we develop a behavioral equivalence and axiomatize it for finite processes. Simple examples are given that highlight the utility of the model