Process-Algebraic Analysis of Timing and Schedulability Properties
In this chapter, we present an overview of how timing information can be embedded in process-algebraic frameworks. We concentrate on the case of discrete-time modeling. We begin by discussing design approaches that have been adopted in different formalisms to model time and time passage, and how the resulting mechanisms interact with one another and with standard untimed process-algebraic operators. We proceed to give an overview of ACSR, a timed process algebra developed for modeling and reasoning about timed, resource-constrained systems. In doing this, ACSR adopts the notion of a resource as a first-class entity, and it replaces maximal progress, employed by other timed process algebras, by the notion of resource-constrained progress. ACSR associates resource-usage with time passage, and implements appropriate semantic rules to ensure that progress in the system is enforced as far as possible while simultaneous usage of a resource by distinct processes is excluded. In addition, ACSR employs the notion of priorities to arbitrate access to resources by competing processes. Finally, we illustrate the use of ACSR for the schedulability analysis of a realistic real-time system problem.