Valérie Roy

Process calculi, from theory to practice: verification tools

We present here two software tools, Auto and Autograph. Both originated directly from the basic theory of process calculi. Both were experimented on well-known problems to enhance their accordance to users expectations.

Auto/Autograph

We describe the Auto and Autograph tools for verification and analysis of concurrent systems in their more recent developments. Auto is dedicated to a philosophy of verification by reduction, based on automata morphisms and quotients. Autograph provides a graphical layout on which to display both terms and informations on terms, back and forth to Auto. We stress the openness aspects of both systems and their interface formats to the outside world. We see this as a contribution to the ever growing collaborative trends between similar tools, mostly under the pressure of national or European Esprit projects.

Modular Compilation of a Synchronous Language

Synchronous languages rely on formal methods to ease the development of applications in an efficient and reusable way. Formal methods have been advocated as a means of increasing the reliability of systems, especially those which are safety or business critical. It is still difficult to develop automatic specification and verification tools due to limitations like state explosion, undecidability, etc... In this work, we design a new specification model based on a reactive synchronous approach. Then, we benefit from a formal framework well suited to perform compilation and formal validation of systems. In practice, we design and implement a special purpose language (le ) and its two semantics : the behavioral semantics helps us to define a program by the set of its behaviors and avoid ambiguousness in programs’ interpretation; the execution equational semantics allows the modular compilation of programs into software and hardware targets (C code, Vhdl code, Fpga synthesis, Verification tools). Our approach is pertinent considering the two main requirements of critical realistic applications : the modular compilation allows us to deal with large systems, the model-driven approach provides us with formal validation.

Modeling Ship Behavior based on Hidden Markov Models

Since 2001, works in the field of security have been considerably growing. All over the word, public places as markets, parkings, hotels, metro and train stations are permanently threatened by terroristic events. For this reason, researches are working every day to meet the need of security. In this article, we have been interested in securing harbors, equipements and people from any threatening event by studying, classifying and recognizing ships behaviors. We propose to use the probabilistic approach Hidden Markov Models (HMM) because of its promising performance in the field of behaviors learning and recognition. The idea is to gather the map of the port as well as ships trajectories in order to construct a set of models of all ships behaviors. Then, this set is exploited to classify every new ship trajectory moving in the harbor. Map of the harbor allowed the initialization of HMM models of ships behaviors, then the well-known Baum-Welch algorithm was chosen to learn models from ships trajectories obtained from port and finally the forward algorithm was used to classify and recognize every new ship behavior.

The FC2TOOLS Set

We describe a set of modular extensions to our Auto/Graph verification toolset for networks of communicating processes. These software additions operate from a common file exchange format for automata and networks, called fc2. Tool functionalities comprise graphical depiction of objects, global model construction from hierarchical descriptions, various types of model reductions and of verification of simple modal properties by observers, counterexample production and visualisation. We illustrate typical verification sessions conducted on usual academic examples. Based on previous experience of drastic state explosion problems we aim here at efficiency in implementation. We use both explicit representation techniques and implicit techniques such as BDDs, with functional overlap at places.

Behavior Analysis Modulus for harbor security

This paper focuses on protecting harbor by monitoring the behavior of ships moving in the harbor. In particular, we propose to combine a probabilistic Hidden Markov Model approach with a formal language approach to model and recognize usual and unusual ship behavior. The probabilistic approach was mainly used to recognize usual ship behavior. However, the reactive approach was used to recognize abnormal ship behavior and classify it into aggressive and transgressive. By combining probabilistic and reactive approaches, we conceived a Behavior Analysis Modulus that we called BAM. It is a decision support system for port team security that aims to generate security advice on ships as they enter into the harbor.

TOWARDS AN INTEGRATED CONCEPTION OF HYBRID DYNAMICAL SYSTEMS

Hybrid dynamical systems are composed of continuous-time dynamical parts, mixed with event-driven parts. Most of the time, both parts are designed separately using specific techniques of each domain, and integrated a posteriori in an application-specific manner. This approach is restrictive in that it does not exhibit a hybrid global model of the designed system, that would though be required for analysis and behavior-checking to take place. In this paper, we discuss and illustrate our approach of hybrid systems modeling, that is based on the obvious statement that both domains (dynamical and event-driven) must be clearly considered in an integrated manner from the very beginning of the design. In our example, we exhibit a draft formal framework for hybrid system modeling, that would allow for verification techniques. For that purpose, we take advantage of the recently developed techniques and tools, in both areas. The numerical computation laboratory - matlab - that we chose for the dynamical system part design, fits perfectly with our goals. But the reactive synchronous language chosen - Esterel -, if it actually fits with the event-driven part specification, exhibits some weaknesses when dealing with data and values, that are needed when interfacing both parts together.