C.A. Vissers

Formal description techniques

Early in the development of OSI, it was recognized that formal description techniques (FDTs) would be required to accomplish the goals of OSI. This paper is a brief history and a report on the status of the work of ISO/TC97/SC16/WG1 ad hoc Group on Formal Description Techniques. The group comprises three subgroups: the first working on architectural concepts; the second, on an FDT based on extended finite-state machines; and the third, on an FDT based on temporal ordering of interaction primitives. An overview of the techniques developed by each of these groups, as of December, 1982, is presented.

Specification styles in distributed systems design and verification

Substantial experience with the use of formal specification languages in the design of distributed systems has shown that finding appropriate structures for formal specifications presents a serious, and often underestimated problem. Its solutions are of great importance for ensuring the quality of the various designs that need to be developed at different levels of abstraction along the design trajectory of a system. This paper introduces four specification styles that allow us to structure formal specifications in different ways: the monolithic, the constraint-oriented, the state-oriented, and the resource-oriented style. These styles have been selected on the basis of their suitability to express design concerns by structuring specifications and their suitability to pursue qualitative design principles such as generality, orthogonality, and open-endedness. By giving a running example, a query-answer service, in the ISO specification language LOTOS, these styles are discussed in detail. The support of verification and correctness preserving transformation by these styles is shown by verifying designs, expressed in different styles, with respect to each other. This verification is based on equational laws for (weak) bisimulation equivalence.

LOTOSphere: Software Development with Lotos

Preface. Part I: Introduction and Overview. 1. LOTOSphere, an Attempt towards a Design Culture C.A. Vissers, L. Ferreira Pires, J. van de Lagemaat. 2. The LOTOSphere Design Methodology J. Quemada, A. Azcorra, S. Pavon. 3. Design and Implementation Strategies J. Schot, L. Ferreira Pires. 4. Getting to Use the LOTOSphere Integrated Tool Environment (LITE) J.A. Manas. 5. LOTOS Industrial Applications. 6. Applying LOTOS to OSI Application Layer Protocols R.E. Booth. Part II: Specification and Transformation. 7. LOTOS Specification Style for OSI K.J. Turner, M. van Sinderen. 8. Correctness Preserving Transformations for the Early Phases of Software Development T. Bolognesi, D. De Frutos, R. Langerak, D. Latella. 9. Correctness Preserving Transformations for the Late Phases of Software Development A. Fantechi, B. Mekhanet, E. Najm, P. Cunha, J. Queiroz. 10. A Case Study on Protocol Design J.-P. Courtiat, D.-E. Saidouni. Part II: Analysis. 11. Executing LOTOS Specifications: the SMILE Tool H. Eertink. 12. A Pragmatic Approach to Verification, Validation and Compilation T. Miguel, A. Azcorra, J. Quemada, J.A. Manas. 13. An Exercise in Protocol Verification S. Gnesi, E. Madelaine, G. Ristori. 14. A Tool for Checking ADT Completeness and Consistency D. Wolz. 15. Deriving Tests from LOTOS Specifications T. Bolognesi, D. De Frutos, R. Langerak, D. Latella. Part IV: Implementation. 16. The COLOS Compiler K. Warkentyne, E. Dubuis.17. TP Protocol from Specification to Implementation I. Widya, G.-J. van der Heijden, F. Juillot. 18. Realization of CCR in C V. Jones. 19. ALTO: an Interactive Transformation Tool for LOTOS and LOTOMATION E. Najm, A. Serhrouchni, A. Lakas, E. Madelaine, R. de Simone. Part V: Graphical LOTOS. 20. G-LOTOS: a Graphical Language for Concurrent Systems T. Bolognesi, E. Najm, P.A.J. Tilanus. 21. GLOW 3.0 -- a Graphical LOTOS Browser T. Bolognesi, M. Caneve, E. Salvatori. Part VI: LOTOS Enhancements. 22. Enhancements of LOTOS E. Brinksma, G. Leih. 23. Data Specifications in Modular LOTOS R. Roth, J. de Meer, S. Storp. Index.

On the role of basic design concepts in behaviour structuring

This paper presents some basic design concepts for the design of open distributed systems. These concepts should form the basis for the development of effective design methodologies. The paper discusses how design concepts, such as interaction, action and causality relation, can be used for modelling and structuring behaviours of functional entities in a distributed environment. The paper also addresses some consequences of the application of these design concepts such as the choice of language elements and operations to represent behaviour structure, the structuring of the design process, and the definition of design operations for behaviour refinement.

A design model for open distributed processing systems

This paper proposes design concepts that allow the conception, understanding and development of complex technical structures for open distributed systems. The proposed concepts are related to, and partially motivated by, the present work on Open Distributed Processing (ODP). As opposed to the current ODP approach, the concepts are aimed at supporting a design trajectory with several, related abstraction levels. Simple examples are used to illustrate the proposed concepts.

Protocol design and implementation using formal methods

This paper reports on a number of formal methods that support correct protocol design and implementation. These methods are placed in the framework of a design methodology for distributed systems that was studied and developed within the ESPRIT II Lotosphere project (2304). The paper focuses on design methods for synthesizing protocols by successive application of correctness-preserving LOTOS transformations. This transformational approach is described in some detail and is illustrated with a protocol design example. The paper concludes with some suggestions for relating design methods to milestones in the protocol design and implementation processes.

Lotosphere an attempt towards a design culture

Competitiveness, a major concern of industrial companies, is usually determined by a large number and diversity of factors. Product range, marketing approach, stock control, logistics, cost control, and advertising strategy are just a few of them. The Lotosphere project has focussed on some aspects of competitiveneness that underly many of these factors, viz. productivity and product quality.

Overview of the Lotosphere Design Methodology

This paper presents the direction of work in the Lotosphere Design Methodology. It first examines some basic concepts in distributed systems’ design and then identifies areas for further research and development. In this paper we define and analyse the needs of the design process for distributed systems, in order to determine how the use of a formal design language as LOTOS can improve this process. A top-down view of the design trajectory is used in order to introduce the design goals, and related definitions and concepts. In this context we discuss the role of abstraction as the concept that supports step-wise refinement, and the role of design languages, as the means to represent the relevant properties of a system. A more elaborated design trajectory takes into consideration the deviation cases from the straight top-down model. This analysis ends up at the level of design steps, at which design concerns are identified as the areas of interest: the design methods that comprise the methodology. The paper intends to provide a framework for the effective use of Formal Description Techniques (FDTs) in distributed system design, which is to be applied in the scope of the ESPRIT II Lotosphere Project (Project 2304).

Interface, a dispersed architecture

Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a precise definition of an interface. With this definition as starting point, the inherent structure of an interface is developed. A horizontal and vertical partitioning strategy, based on one functional entity per partition and described by a state description, is used to specify the structure. This method allows unambiguous specification, interpretation, and implementation, and allows a much easier judgement of the quality of an interface. The method has been applied to a number of widely used interfaces.

Formal Specification in OSI

Formal Description Techniques (FDTs) that should be capable to express the OSI Protocols and Services are confronted with unprecedented requirements in terms of the abstraction level at which the OSI architectural concepts need to be expressed as well as the high complexity of the OSI standards.