José A. Mañas

Tool support to implement LOTOS formal specifications

Abstract LOTOS is a specification language that aims to describe the dynamic behavior of complex systems. To a large extent, LOTOS semantics is operational, which gives an opportunity to execute the specifications. There may be several targets in specification execution, three of which are considered in the paper: rapid prototyping, system testing, and real product derivation. The outstanding problem is to map abstract entities onto real entities, both to effectively act on the environment, and to allow the environment to influence specification behavior. For a final product, performance must be assessed too, as well as other non-functional requirements. The paper describes the opportunities provided by TOPO, a compiler from LOTOS into either C or Ada code. Supported features are described and wrapped into a method. Performance figures are provided too, in order to make estimates on realization performance after the specification style.

Λβ: a Virtual LOTOS Machine

LOTOS behaviour semantics are usually presented in a declarative style that permits to evaluate which events are possible at each stage, and which is the behaviour after an event occurs. In order to generate code that implements these operational semantics, an imperative model is very convenient for efficiency. A virtual machine (β-machine for LOTOS Behaviour Machine) is presented in this paper that provides such an imperative point of view, but still keeps independent of implementation details, effectively providing an intermediate representation for either interpretation or generation of code for any systems programming language. An abstract model of execution is presented, and then the virtual machine is presented by describing its instructions, the relationship to LOTOS constructs, and its dynamic semantics. C code generation is briefly commented too.

A PRAGMATIC APPROACH TO VERIFICATION, VALIDATION AND COMPILATION

The scope of this work is the industrial application of the Lotosphere methodology for distributed system design. The operational aspects of the Lotosphere methodology are described in [D02].

Getting to Use the Lotosphere Integrated Tool Environment (Lite)

The Lotosphere project has focused on developing both a methodology and a tool set for making the use of LOTOS industrially effective in product development. The methodology (which is described in Chapters 2 and 3) and the tools are strongly coupled, each tool having its room in the methodology as indicated in chapter 1. In this chapter we shall concentrate on the tools, but we shall do it by means of a running example that refers to the main phases of the methodology. Figure 1 shows the tour we plan to follow for demonstrating some of the lite tools.

Tool Demonstration: A Cross Compiling Experiment: A PC Implementation of a LOTOS Spec

An abracadabra protocol entity is implemented in a PC running MS-DOS. The protocol was initially specified using LOTOS. After annotating it to add implementation details, a LOTOS to C compiler, TOPO, is used to generate code. This code is ported to a PC. The result is an autonomous system that will be used to demonstrate conformance testing scenarios involving the use of formal description techniques.