Revisiting sequential composition in process calculi

International audienceThe article reviews the various ways sequential composition is defined in traditional process calculi, and shows that such definitions are not optimal, thus limiting the dissemination of concurrency theory ideas among computer scientists. An alternative approach is proposed, based on a symmetric binary operator and write-many variables. This approach, which generalizes traditional process calculi, has been used to define the new LNT language implemented in the CADP toolbox. Feedback gained from university lectures and real-life case studies shows a high acceptance by computer-science students and industry engineers

Precongruence Formats for Decorated Trace Preorders

This paper explores the connection between semantic equivalences and preorders for concrete sequential processes, represented by means of labelled transition systems, and formats of transition system specifications using Plotkin's structural approach. For several preorders in the linear time -- branching time spectrum a format is given, as general as possible, such that this preorder is a precongruence for all operators specifiable in that format. The formats are derived using the modal characterizations of the corresponding preorders. 1. Introduction Structural operational semantics [24] provides process algebras and specification languages with an interpretation. It generates a (labelled) transition system in which states are the closed terms over a (single-sorted, first-order) signature, and transitions between states may be supplied with labels. The transition relation is obtained from a transition system specification (TSS), this being a set of proof rules called transition rules..