Search

Jacques Perriault was a pioneer in computer science at a time it scarcely existed. A major theme that runs throughout his work is the interaction between technology and society. His thesis The logic of use. Essay on communicating machines shows the different ways in which users follow or twist the prophetic proposals of inventors. Looking at pupils as well as e-learning adults using NTIC devices, he insisted on the consequences on cognition and the risk of social fracture. He embedded his analysis of the Technology Imprint on Société in a long term history (Memories of Shadow and Sound. An Archeology of Audiovisual Devices). From this historical perspective, a forward looking vision had him involved in the creation of international standards to be negotiated and built with respect to the end users, so as to be considered as public goods. His wide- reaching intellectual curiosity and his endless transgressions of disciplinary boundaries explain his atypical career. Many researchers are grateful to him for his generosity in suggesting new perspectives while endlessly opening up new and unexpected avenues of research.

Abstract: Good scheduling policies for distributed embedded applications are required for meeting hard real time constraints and for optimizing the use of computational resources. We study the quasi-static scheduling problem in which (uncontrollable) control flow branchings can influence scheduling decisions at run time. Our abstracted distributed task model consists of a network of sequential processes that communicate via point-to-point buffers. In each round, the task gets activated by a request from the environment. When the task has finished computing the required responses, it reaches a pre-determined configuration and is ready to receive a new request from the environment. For such systems, we prove that determining the existence of a scheduling policy that guarantees upper bounds on buffer capacities is undecidable. However, we show that the problem is decidable for the important subclass of “data-branching” systems in which control flow branchings are exclusively due to data-dependent internal choices made by the sequential components. This decidability result exploits ideas derived from the Karp and Miller coverability tree for Petri nets as well as the existential boundedness notion of languages of message sequence charts. [ABSTRACT FROM AUTHOR]

The closed cover technique is a technique for verifying progress for two communicating finite state machines exchanging messages over two lossless and FIFO channels. It was first introduced by Gouda. A set of global states is called a closed cover if it satisfies some conditions given in Gouda's paper, but an intuitive description of why one of the conditions is necessary is not provided. It is found that the definition of a closed cover is too restrictive in one paper and incorrect in the other. This correspondence clarifies this and suggests improved definitions for a closed cover which are increasingly less restrictive. [ABSTRACT FROM AUTHOR]