Piotr Dembinski

An introduction to Estelle: a specification language for distributed systems

Abstract Estelle is a Formal Description Technique, defined within ISO (International Organization for Standardization) for specification of distributed, concurrent information processing systems. In particular, Estelle can be used to describe the services and protocols of the layers of Open Systems Interconnection (OSI) architecture defined by ISO. Its present ISO status is Draft International Standard (DIS 9074). The article outlines syntactic and semantic aspects of this description technique.

√erics: a tool for verifying timed automata and estelle specifications

The paper presents a new tool for automated verification of Timed Automata as well as protocols written in the specification language Estelle. The current version offers an automatic translation from Estelle specifications to timed automata, and two complementary methods of reachability analysis. The first one is based on Bounded Model Checking (BMC), while the second one is an on-the-fly verification on an abstract model of the system.

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.

Enumeration Protocol in Estelle: an exercise in stepwise development

The paper sketches a design process that starts with a mathematical solution of the enumeration problem and ends up with a distributed, efficient, and successfully terminating protocol in the specification language Estelle. The subsequent versions of the protocol are obtained from their predecessors by well controlled and small modifications that (almost) obviously preserve correctness. The target, successful (successful with arbitrarily high probability) solution allows forgetting theoretical “impossibility results”, which prove non-existence of such successful distributed solutions for some classes of networks.

Semantics of timed concurrent systems

A truly concurrent and timeless semantics is proposed for a composition of sequential, non-deterministic processes with asynchronous communication. It is shown when this semantics differs from simple interleaving. Implementation-dependent time constraints determine a subset of all computations of the timeless semantics. This set is precisely characterized for given constraints. It is shown how the same set may be generated by a timed transition system, i.e., how to simulate time-constrained and concurrent computations by sequential, non-deterministic system. The paper includes a proof of the correctness of such simulation.

The taming of the pointer

The existence of pointers in a higher-level programming language has been considered by many as a serious, if not insurmountable, impediment to software reliability. This paper seeks to show that most of the problems created by the use of the pointer are due to an implementation level pointer definition. A new approach is proposed which treats the pointer type in a way consistent with other data types. An example is given of how formal program verification methods can be applied to programs manipulating structures created with pointers if the introduced definition is used. A discussion is given of some implications of the adopted concepts and how they are related to the question of data representation and such notions as data abstraction.

Simulation of Security Protocols based on Scenarios of Attacks

In this paper we offer a methodology allowing for simulation of security protocols, implemented in the higher-level language Estelle, using scenarios designed for external attacks. To this aim we apply a translation of specifications of security protocols from Common Syntax to Estelle and an encoding of schemes of attacks into Estelle scenarios. We show that such an intelligent simulation may efficiently serve for validating security protocols.

Automated Verification of Infinite State Concurrent Systems

The paper shows how to use partitioning techniques to generate abstract state spaces (models) preserving similarity and injectivity. Since these relations are weaker than bisimilarity and surjectivity, our algorithms generate smaller models. This method can be applied for improving several existing partitioning algorithms used for generating finite models of concurrent programs, Time Petri Nets and Timed Automata.