Chapter 13 – Dependability engineering. The objective of this chapter is to discuss processes and techniques for developing highly dependable systems. When you have read this chapter you will: understand how system dependability can be achieved by using redundant and diverse components; know how dependable software processes contribute to the development of dependable software; understand how different architectural styles may be used to implement software redundancy and diversity;. | Chapter 13 – Dependability engineering Lecture 1 1 Chapter 13 Dependability Engineering Topics covered Redundancy and diversity Fundamental approaches to achieve fault tolerance. Dependable processes How the use of dependable processes leads to dependable systems Dependable systems architectures Architectural patterns for software fault tolerance Dependable programming Guidelines for programming to avoid errors. Chapter 13 Dependability Engineering 2 Software dependability In general, software customers expect all software to be dependable. However, for non-critical applications, they may be willing to accept some system failures. Some applications (critical systems) have very high dependability requirements and special software engineering techniques may be used to achieve this. Medical systems Telecommunications and power systems Aerospace systems 3 Chapter 13 Dependability Engineering Dependability achievement Fault avoidance The system is developed in such a way that human error . | Chapter 13 – Dependability engineering Lecture 1 1 Chapter 13 Dependability Engineering Topics covered Redundancy and diversity Fundamental approaches to achieve fault tolerance. Dependable processes How the use of dependable processes leads to dependable systems Dependable systems architectures Architectural patterns for software fault tolerance Dependable programming Guidelines for programming to avoid errors. Chapter 13 Dependability Engineering 2 Software dependability In general, software customers expect all software to be dependable. However, for non-critical applications, they may be willing to accept some system failures. Some applications (critical systems) have very high dependability requirements and special software engineering techniques may be used to achieve this. Medical systems Telecommunications and power systems Aerospace systems 3 Chapter 13 Dependability Engineering Dependability achievement Fault avoidance The system is developed in such a way that human error is avoided and thus system faults are minimised. The development process is organised so that faults in the system are detected and repaired before delivery to the customer. Fault detection Verification and validation techniques are used to discover and remove faults in a system before it is deployed. Fault tolerance The system is designed so that faults in the delivered software do not result in system failure. 4 Chapter 13 Dependability Engineering The increasing costs of residual fault removal 5 Chapter 13 Dependability Engineering Regulated systems Many critical systems are regulated systems, which means that their use must be approved by an external regulator before the systems go into service. Nuclear systems Air traffic control systems Medical devices A safety and dependability case has to be approved by the regulator. Therefore, critical systems development has to create the evidence to convince a regulator that the system is dependable, safe and secure. Chapter 13 Dependability
