Efficient Method Developed by Thales for Safety Evaluation of Real-to-Integer Discretization and Overflows in SIL4 Software

Abstract

This book presents real examples of the formal techniques called?abstract interpretation? currently being used in various industrialfields: railway, aeronautics, space, automotive, etc.The current literature seems to only provide very general books on theformal techniques. The purpose of this book is to present students andresearchers, in a single book, with the wealth of experience of peoplewho are intrinsically involved in the realization and evaluation ofsoftware-based safety critical systems. As the authors are people currently working withinthe industry, the usual problems of confidentiality, which can occur with other books, isnot an issue and so makes it possible to supply new useful information (photos,architectural plans, real examples).This chapter introduce a method based on interval arithmetic to analyse computation risks due to integer conversions of an infinite precision specification. The work also takle the overflow and division by zero problems in arithmetic computation chains. The method was developed and applied within the context of railway command and control systems and the chapter present a case study on a speed control algorithm