Pierre Azéma

Petri nets as a common tool for design verification and hardware simulation

An APL simulation is developped in the case of parallel systems which communicate with the environment. This method using interpreted PETRI nets, helps the design verification.

Testability of a Communicating System Through an Environment

Testing of a component embedded in a whole system is addressed. The component is not as easy to check as when taken in isolation. The notion of conformance, as introduced by E. Brinksma and G. Scollo, is extended to formalize testing through an environment that does not allow some non conforming implementations to be discarded. A method enabling embedded systems testability to be characterized is proposed. It is based on the refusal graph whose arcs are labeled by events and nodes by subsets of events. An approach is presented to identify erroneous implementations. In particular, the least erroneous implementations discarded by testing through environment are defined and computed.

Petri net based models for the specification and validation of protocols

The main interest which comes from the use of state based approaches is their easy acceptance by users. People understand and become able to use them in a rather short time, beginning with problems or parts of protocols of a given simplicity and then going to use more complex nets.

Requirement Analysis for Communication Protocols

PROLOG Interpreted Predicate Net (PIPN) is a software tool for the specification and analysis of communications in distributed computing systems. Labelled Predicate/Transition Nets are embedded into a logic programming environment. Executable specifications are defined by labelled transition systems. Observational equivalence and temporal logic techniques are concurrently applied.

Verifying Communication Protocols Via Testing-Projection

A method is provided to reduce a labeled transition system while preserving testing equivalence. This method uses the refusal graph, an abstract structure for representing communicating systems, and two transformations for deriving a refusal graph from a labeled transition system and vice-versa. The reduced systems are in normal form for the testing equivalence and are minimal with respect to the bisimulation equivalence.

Selective generation of symmetrical test cases

In this paper, system symmetries are shown to efficiently reduce the size of the complete test suite required for checking the implementation conformance. The reduction is obtained by eliminating all the symmetrical test cases during the generation of the test suite. The method is applied over the theoretical model of conformance testing developed by [Bri88] using the implementation relation conf. In this model, symmetries are defined as bijective renamings of actions which preserve conformance properties, and allow test folding. The symmetries may concern either architectural properties, or execution sequences, or data structures, respectively. By exploiting data or state symmetries, infinite complete test suites may be reduced into finite one.

Distributed coin tossing

This paper presents algorithms for distributed coin tossing. Distributed coin tossing furnishes a symmetrical way to break the symmetry in a distributed system. They allow the conflicts arising from competing remote sites to be overcome in a fair (equiprobable) manner: any site has an equal chance of being selected. It as also shown how these algorithms may be used to obtain a total order between competing sites of a system. Moreover, in each case the outputs of our algorithms are totally unpredictable.<<ETX>>

High level transition systems for communicating agents

This paper presents an agent-oriented formalism based on Logic Programming and Predicate/Transition Nets. The problem of moving philosophers is used as application example. A distributed system is considered as a result of composition of agents, which are instances of predefined classes. A main objective is to describe dynamic systems of communicating agents.

Permutable Agents in Process Algebras

Within the framework of symmetrical systems, an extension of CCS [6], so-called PCCS, is described. PCCS equips CCS with the concept of pool of agents by means of the explicit structure of Pool expressions. The symmetries whithin a Pools of agents may then be used to simplify the validation process of concurrent systems.

A formal assessment of synchronous testability for communicating systems

A testability assessment approach for multicomponent systems is proposed within the framework of formal description techniques. The approach relies on the formal definition of implementation conformance with respect to a given specification. It provides measures of user confidence and guidelines for an automatic design analysis. Both items are based on test requirements. The proposed technique for testability assessment formalizes the common-sense statement that testability of a component is degraded when this component cannot be tested in isolation. Furthermore, it gives a precise answer to the question: What are the limits of a test taking into consideration the constraints of a given environment?.<<ETX>>