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Über dieses Buch

W.J.Quirk 1.1 Real-time software and the real world Real-time software and the real world are inseparably related. Real time cannot be turned back and the real world will not always forget its history. The consequences of previous influences may last for a long time and the undesired effects may range from being inconvenient to disastrous in both economic and human terms. As a result, there is much pressure to develop and apply techniques to improve the reliability of real-time software so that the frequency and consequences of failure are reduced to a level that is as low as reasonably achievable. This report is about such techniques. After a detailed description of the software life cycle, a chapter is devoted to each of the four principle categories of technique available at present. These cover all stages of the software development process and each chapter identifies relevant techniques, the stages to which they are applicable and their effectiveness in improving real-time software reliability. 1.2 The characteristics of real-time software As well as the enhanced reliability requirement discussed above, real-time software has a number of other distinguishing characteristics. First, the sequencing and timing of inputs are determined by the real world and not by the programmer. Thus the program needs to be prepared for the unexpected and the demands made on the system may be conflicting. Second, the demands on the system may occur in parallel rather than in sequence.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract
Real-time software and the real world are inseparably related. Real time cannot be turned back and the real world will not always forget its history. The consequences of previous influences may last for a long time and the undesired effects may range from being inconvenient to disastrous in both economic and human terms. As a result, there is much pressure to develop and apply techniques to improve the reliability of real-time software so that the frequency and consequences of failure are reduced to a level that is as low as reasonably achievable.
W. J. Quirk

2. Software Reliability and the Software Life Cycle

Abstract
Computer systems are planned or are already in use in a variety of areas involving online, real-time control.
S. Bologna, W. J. Quirk

3. Structural Analysis and Proof

Abstract
There are many techniques which can be used to analyse programs, and to demonstrate program properties, which do not require any form of program execution.
J. R. Taylor, U. Voges, P. Puhr-Westerheide, W. J. Quirk

4. Systematic Testing

Abstract
This chapter deals with different techniques which can be applied for testing the final program in a systematic manner. Systematic does not relate to the combination of methods, but refers to each single method. It is mainly in contrast to probabilistic testing.
U. Voges, J. R. Taylor

5. Statistical Testing of Real Time Software

Abstract
In view of the difficulties with real-time software verification that were discussed in the earlier chapters of this book the reader might ask wether it can be easier, and therefore cheaper, to use probabilistic methods instead of systematic ones. As we will see later, however, it is normally quite costly to apply statistical testing for singular (i.e. not diverse) software system. This is mainly due to the large number of test runs that are required to achieve quantitative results which are acceptable for a system of any practical importance. This leads to the recommendation to use statistical tests only as a complement to systematic verification.
W. Ehrenberger

6. Simulation and System Validation

Abstract
A simulator can be defined as any device which calculates, emulates or predicts the behaviour of another device, or some aspect of the behaviour of the world. Simulators can be implemented using either analogue or digital computers. In the field of real-time system validation, they are used to:
  • simulate the real world to provide inputs to the system
  • simulate the real world for evaluating the outputs from the system
  • simulate the system itself to evaluate its acceptability.
S. Bologna, W. J. Quirk, J. R. Taylor

7. Conclusion

Abstract
In addition to the critiques of the individual techniques of real-time software verification and validation in the previous chapters, some general views about their applicability and their future importance seem to be in order. This chapter therefore will emphasise some of the aspects already mentioned and try to build some sort of a roof over the other chapters.
W. D. Ehrenberger

Backmatter

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