Basic concepts and taxonomy of dependable and secure computing

This paper gives the main definitions relating to dependability, a generic concept including a special case of such attributes as reliability, availability, safety, integrity, maintainability, etc. Security brings in concerns for confidentiality, in addition to availability and integrity. Basic definitions are given first. They are then commented upon, and supplemented by additional definitions, which address the threats to dependability and security (faults, errors, failures), their attributes, and the means for their achievement (fault prevention, fault tolerance, fault removal, fault forecasting). The aim is to explicate a set of general concepts, of relevance across a wide range of situations and, therefore, helping communication and cooperation among a number of scientific and technical communities, including ones that are concentrating on particular types of system, of system failures, or of causes of system failures.     

Faulty-Tolerant Computing: An Overview

The discipline of fault-tolerant computing would be unnecessary if computer hardware and programs would always behave in perfect agreement with the designer's or programmer's intentions. However, imperfections of computer systems and program "bugs" have been with us since the first computer was built, and fault tolerance will remain an important objective as long as computers are in demand.     

Performability enhancement of fault-tolerant software

Model-based performability evaluation is used to assess and improve the effectiveness of fault-tolerant software. The evaluation employs a measure that combines quantifications of performance and dependability in a synergistic manner, thus capturing the interaction between these two important attributes. The specific systems evaluated are a basic realization of N-version programming (NVP) (N =3) along with variants thereof. For each system, its corresponding stochastic process model is constructed in two layers, with performance and dependability submodels residing in the lower layer. The evaluation results reveal the extent to which performance, dependability, and performability of a variant are improved relative to the basic NVP system. More generally, the investigation demonstrates that such evaluations are indeed feasible and useful with regard to enhancing software performability     

Toward systematic design of fault-tolerant systems

After 30 years of study and practice in fault tolerance, high-confidence computing remains a costly privilege of several critical applications. It is time to explore ways to deliver high-confidence computing to all users. The speed of computing will ultimately be limited by the laws of physics, but the demand for affordable high-confidence computing will continue as long as people use computers to enhance the quality of their lives. Eventually, one enterprising chip builder will deliver the first fault-tolerant microprocessor at a competitive price, and soon thereafter fault tolerance will be considered as indispensable to computers as immunity is to humans. The remaining manufacturers will follow suit or go the way of the dinosaurs. Once again, Darwin will be proven right