Introduction to the ISO specification language LOTOS

LOTOS is a specification language that has been specifically developed for the formal description of the OSI (Open Systems Interconnection) architecture, although it is applicable to distributed, concurrent systems in general. In LOTOS a system is seen as a set of processes which interact and exchange data with each other and with their environment. LOTOS is expected to become an ISO international standard by 1988

Rigorous object-oriented analysis

Object-oriented methods for analysis, design and programming are commonly used by software engineers. Formal description techniques, however, are mainly used in a research environment. We have investigated how rigour can be introduced into the analysis phase of the software development process by combining object-oriented analysis (OOA) methods with formal description techniques. The main topics of this investigation are a formal interpretation of the OOA constructs using LOTOS, a mathematical definition of the basic OOA concepts using a simple denotational semantics and a new method for object- oriented analysis that we call the Rigorous Object-Oriented Analysis method (ROOA). The LOTOS interpretation of the OOA concepts is an intrinsic part of the ROOA method. It was designed in such a way that software engineers with no experience in LOTOS, can still use ROOA. The denotational semantics of the concepts of object-oriented analysis illuminates the formal syntactic transformations within ROOA and guarantees that the basic object- oriented concepts can be understood independently of the specification language we use. The ROOA method starts from a set of informal requirements and an object model and produces a formal object-oriented analysis model that acts as a requirements specification. The resulting formal model integrates the static, dynamic and functional properties of a system in contrast to existing OOA methods which are informal and produce three separate models that are difficult to integrate and keep consistent. ROOA provides a systematic development process, by proposing a set of rules to be followed during the analysis phase. During the application of these rules, auxiliary structures are created to help in tracing the requirements through to the final formal model. As LOTOS produces executable specifications, prototyping can be used to check the conformance of the specification against the original requirements and to detect inconsistencies, omissions and ambiguities early in the development process

Modelling Digital Logic in SDL

The specification of digital logic in SDL (Specification and Description Language) is investigated. A specification approach is proposed for multi-level descriptions of hardware behaviour and structure. The modelling method exploits features introduced in SDL-92. The approach also deals with the specification, analysis and simulation of timing aspects at any level in the specification of digital logic

Specification and Verification of Synchronous Hardware using LOTOS

This paper investigates specification and verification of synchronous circuits using DILL (Digital Logic in LOTOS). After an overview of the DILL approach, the paper focuses on the characteristics of synchronous circuits. A more constrained model is presented for specifying digital components and verifying them. Two standard benchmark circuits are specified using this new model, and analysed by the CADP toolset (Cæsar/Aldébaran Development Package)

Model-based verification of a security protocol for conditional access to services

peer reviewedWe use the formal language LOTOS to specify and verify the robustness of the Equicrypt protocol under design in the European OKAPI project for conditional access to multimedia services. We state some desired security properties and formalize them. We describe a generic intruder process and its modelling, and show that some properties are falsified in the presence of this intruder. The diagnostic sequences can be used almost directly to exhibit the scenarios of possible attacks on the protocol. Finally, we propose an improvement of the protocol which satisfies our properties

A Service-Based Component Model: Formalism, Analysis and Mechanization

Component-Based Software Engineering (CBSE) is one of the approaches to master the development of large scale software. In this setting, the verification concern is still a challenge. The objective of our work is to provide the designer of components-based systems with the methods to assist his/her use of the components. In particular, the current work adresses the composability of components and their services. A component model is presented, based on services. An associated simple but expressive formalism is introduced; it describes the services as extended LTS and their structuring as components. The composition of components is mainly based on service composition and encapsulation. The composability of component is defined from the composability of services. To ensure the correctness of component composition, we check that an assembly is possible via the checking of the composabiblity of the linked services, and their behavioral compatibility. In order to mechanize our approach, the services and the components are translated into the MEC and LOTOS formalism. Finally the MEC and LOTOS CADP toolbox is used to perform experiments