Refinement of Actions in a Real-Time Process Algebra with a True Concurrency Model

AbstractIn this paper, we develop techniques of action refinement in a real-time process algebra that allows urgent interactions to model timeout. Semantic counterpart is carried out in a real-time non-interleaving causality based setting, timed bundle event structures. We show that our refinement notions have the following nice properties: the observable behaviour of the refined system can be inferred compositionally from the observable behaviour of the original system and from the observable behaviour of the processes substituted for the actions; the timed extensions of observational pomset trace equivalence and observational history preserving bisimulation equivalence are both congruences under our refinement; and the syntactic and semantic refinements coincide up to the aforementioned equivalence relations with respect to a cpo-based denotational semantics

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