Jean-Michel Ayache

Petri nets are good for protocols

This paper is intended to survey the applicability of Petri nets for protocol, as well as for service specification and validation. At the specification level, different classes of nets are introduced, and emphasis is given to the modular specification of a protocol layer. At the validation level, the analysis techniques implemented in the CAD package OGIVE/OVIDE are presented, and are used in order to prove safety and progress properties of a protocol layer. Finally, the specification and validation of the ISO Transport protocol is chosen as a significant example of the proposed design methodology.

SOFTWARE AND PROTOCOLS IN REBUS. A DISTRIBUTED REAL-TIME CONTROL SYSTEM

REBUS is a robust and fault tolerant cooperation system for a local real time control microcomputer network. It is being developed at the LAAS in connexion with the industrial real time control system MODUMAT 800 of SCHLUMBERGER-EUROPE. Based on a general hardware architecture, the design of REBUS emphasizes the aspects of cooperation and fault tolerance as required in local real time control networks and it is primarly concerned with the problems of specification, validation and implementation of some standard and specificic protocols. After a short presentation of the hardware architecture, the various software levels are described; they include the operating system kernel of the processors, the line, network and transport layers, and the remote call mechanism. Finally, a tool, the observer, developed for protocol debugging and measure purposes is also presented.

Software and Protocols in Rebus. A Distributed Real-Time Control System

Abstract REBUS is a robust and fault tolerant cooperation system for a local real time control microcomputer network. It is being developed at the LAAS in connexion with the industrial real time control system MODUMAT 800 of SCHLUMBERGER-EUROPE. Based on a general hardware architecture, the design of REBUS emphasizes, the aspects of cooperation and fault tolerance as required in local real time control networks and it is primarly concerned with the problems of specification, validation and implementation of some standard and specificic protocols. After a short presentation of the hardware architecture, the various software levels are described ; they include the operating system kernel of the processors, the line, network and transport layers, and the remote call mechanism. Finally, a tool, the observer, developed for protocol debugging and measure purposes is also presented.

Towards Fault Tolerant Real Time Systems by Using Petri Nets

This paper presents current studies on the use of Petri nets for the design and validation of fault-tolerant distributed systems. Petri nets have been used at the various steps of the design process: initial modeling level definition, static verification and on-line testing. The main context of these studies involves distributed systems for which a crucial problem concerns the ability for the model to design and validate the consistency of the logical behavior for the communication among the processes.