Jean-Pierre Courtiat

Experience with RT-LOTOS, a temporal extension of the LOTOS formal description technique

This paper is devoted to the presentation of the RT-LOTOS formal description technique, which is a formalism suited for applications where concurrency, complex synchronization patterns, asynchronous interactions and timing constraints have to be dealt with together. The paper does not emphasize the details of the RT-LOTOS formal semantics, but intends to explain and illustrate its main features, as well as the main capabilities of its associated software tool rtl. Finally, this paper reports on different applications and case studies that have recently been developed at LAAS-CNRS, some of them in cooperation with the industry.

Proving temporal consistency in a new multimedia synchronization model

This paper introduces a new synchronization model for the formal specification of multimedia documents. By this approach, an user is able to formalize his document by hierarchically composing a set of presentation and constraint objects which are then automatically translated into a complete RT-LOTOS formal specification (RT-LOTOS is a temporal extension of the standard LOTOS Formal Description Technique). Verification of a multimedia document aiming to identify potential temporal inconsistencies is then performed using standard reachability analysis developed and implemented for RT-LOTOS.

Design methodology and formal validation of hypermedia documents

Hypermedia authoring tools usually suffer from a lack of validation capabilities that would make them possible to check a document against temporal inconsistencies. The document design validation methodology proposed in the paper is meant to overcome this problem. The starting point is a document description given in a high-level modeling technique which include hypermedia basic concepts such as nodes (including composite nodes), anchors and links. The high-level document is then translated into a RT-LOTOS formal specification on which simulation, reachability analysis and minimization techniques can be applied for validation purposes. The proposed approach extends an early work to include not only document intrinsic temporal consistency check, but also consistency checking, taking into account the presentation platform.

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.

Formal models for the description of timed behaviors of multimedia and hypermedia distributed systems

Abstract This paper presents two modeling approaches that can be used as a formal basis for designing distributed multimedia and hypermedia systems. Using these approaches, users and designers are able to express formally their multimedia and hypermedia synchronization and time requirements. The two different models considered are Hierarchical Time Stream Petri Nets and RT-LOTOS. It will be shown that both models, starting from a different formal basis, are of interest as they possess complementary advantages and can then be used at different stages of the system life cycle. For instance, HTSPN provides an user-friendly graphical specification framework, whereas RT-LOTOS offers an extensive simulation and validation framework applicable to specifications derived from HTSPN.

ESTIM: an integrated environment for the simulation and verification of OSI protocols specified in ESTELLE

Abstract Formal Description Techniques (FDTs) are an efficient support for protocol engineering, as they permit early detection of design errors through a validation of the protocol formal specification against the expected service. This paper describes the use and design of ESTIM, a tool for the validation of protocols specified using the Estelle∗ FDT which enhances ISO Estelle with a powerful rendezvous mechanism. The original point is that ESTIM combines interactive simulation functionalities for a first debugging level together with a verification approach that allows the automaton characterizing the service provided by a protocol to be derived automatically, starting from the formal specification of that protocol in Estelle∗. The ESTIM tool was prototyped in Standard ML to implement Estelle semantics. It is currently available on SUN Sparc workstations and has successfully been applied to several non-trivial protocols.

A formal approach for the presentation of interactive multimedia documents

This paper presents the on-going work using a formal approach for the design of Interactive Multimedia Documents (IMDs) based on the RT-LOTOS formal description technique. The present work extends this approach proposing the scheduling of IMDs based on a simple and operational model obtained as a result from the reachability analysis. One important breakthrough of this model is that it is a scheduling graph that provides the control of the occurrence of non-deterministic events, such as user interactions, within valid temporal intervals so that the global synchronization constraints of the document can be fulfilled during its presentation. Further on, some scheduling policies are also presented based on this model. Finally, we introduce some characteristics of the player actually available for the presentation of IMDs based on this new model.

Towards a new multimedia synchronization mechanism and its formal definition

The design of a distributed multimedia application involves both temporal and spatial synchronization problems related to the processing, transport, storage, retrieval and presentation of data, sound, still images and video. Within this general framework, the paper aims at defining a new multimedia synchronization mechanism, the so-called conditional delivery mechanism, which appears particularly useful for achieving both intra- and inter-stream synchronization. Main motivations behind this synchronization mechanism are first discussed on a simple example, namely a distributed application in the area of distance and interactive training, and then the details of the mechanism are presented. This presentation starts with an informal discussion on simple examples, which is followed by a formal specification of the mechanism based on the use of a temporal extension of the Formal Description Technique LOTOS.

Revisiting the concept of hypermedia document consistency

The paper generalizes previous works of the authors by revisiting the concept of temporal consistency of hypermedia documents. This generalization relies on the distinction of internal and external non-deterministic events.

Formal methods after 15 years: status and trends: a paper based on contributions of the panelists at the Formal Technique '95 Conference, Montreal, October 1995

ion will be essential features. For others, the need will be the validation of some specific mechanism within a complex system. The availability of efficient tools able to deal with the problem complexity will be a key issue. Finally, others might like to consider formal methods as a means of automating the coding phase of a complex system. The quality of the produced code, in terms of memory occupation and response time, will be a key factor in the assessment of the formal approach selected.