On Observing Dynamic Prioritised Actions in SOC

We study the impact on observational semantics for SOC of priority mechanisms which combine dynamic priority with local pre-emption. We define manageable notions of strong and weak labelled bisimilarities for COWS, a process calculus for SOC, and provide alternative characterisations in terms of open barbed bisimilarities. These semantics show that COWS’s priority mechanisms partially recover the capability to observe receive actions (that could not be observed in a purely asynchronous setting) and that high priority primitives for termination impose specific conditions on the bisimilarities

TPAP An algebra of preemptive processes for verifying real-time systems with shared resources

AbstractThis paper describes a timed process algebra called TPAP. The aim of this algebra is to allow the modelisation of real time embedded processes sharing common resources, and which are sensitive to communication delays and scheduling strategies. Timed broadcasting and process preemption by interruption events are the two main fundamental notions of the algebra. They allow description of schedulers and asynchronous communication mediums, thus which can be taken into account when verifying the real time behaviour of the global system. We first present the process algebra and discuss its properties. A case study from the avionics area is then developed using TPAP, and formally verified by translation into the UPPAAL model checker

Action Refinement in End-Based Choice Settings

The choice operator is essential for the description of action-based reactive systems. If the atomicity of actions is dropped (e.g. by action refinement), one has to decide when the choice is triggered. The standard approach is to trigger the choice when actions start. This thesis examine the alternative approach that the choice is triggered when actions terminate. This end-based choice is motivated and a process algebra, which contains an end-based choice and an action refinement operator, is established. Consistent semantics (operational, denotational, axiomatical) are given. Furthermore, the difference between the start-based and the end-based choice are examined, in particular with respect to equivalence notions. New equivalence are established, since the standard equivalences are not preserved by the end-based action refinement operator