An approach to the reliability optimization of software withredundancy

An approach to the optimization of software reliability is proposed. The emphasis is put on the software redundancy to achieve fault tolerance, i.e. the results of the optimization process are used to determine the optimal structure of the software to be developed. Two optimization models are formulated covering, respectively, modified recovery block scheme and multiversion programming approaches. Both cases are illustrated by simple examples. The models show that it is possible to formulate and solve some software related reliability optimization problems. They further show that the concept of redundancy to achieve fault tolerance (basic for the traditional theory of reliability) can be used in the field of software reliability optimization     

Minimizing the Average Cost of Testing Coherent Systems: Complexity and Approximate Algorithms

The paper deals with the problem of finding optimal testing policy to minimize the average cost of determining the state of a s-coherent system. Computational complexity of this problem is analysed and strong evidence presented that an exact, polynomial-time, algorithm is very unlikely to exist. Instead, three approximate algorithms having polynomial running times are suggested and evaluated. Two of them guarantee reasonably good solutions and might be practical.     

Reliability prediction and estimation of PROLOG programs

This paper presents an approach to reliability prediction and estimation of PROLOG programs, and introduces 2 complexity measures for PROLOG programs. The structural complexity measure refers to the program's static characteristics: size and number of clauses; clause arguments (number and types); and clause types (facts or rules). The operational complexity measure refers to the program's dynamic characteristics: execution frequency of program components; user behavior; and backtracking and recursion. Values of the two measures are used to: (1) predict PROLOG program reliability before testing and in the early testing stages; and (2) estimate the reliability as a function of time, in order to determine whether the reliability objective is achieved. The feature-oriented reliability determination approach leads to improvements in the accuracy of software reliability predictions and estimations     

Fault-tolerant programs and their reliability

The authors review and extend available techniques for achieving fault-tolerant programs. The representation of the techniques is uniform and is illustrated by simple examples. For each technique a fault tree has been developed to derive failure probability from the probabilities of the basic fault events. This allows the subsequent analysis of program-failure causes and the reliability modeling of computer programs. Numerical examples are given to support the comparison of the reviewed techniques. The models can be used to evaluate numerical values of program reliability in a relatively simple way. The models deal with program reliability for a single run, which seems more practical and straightforward than dealing with distributions as for hardware systems. Evaluations obtained by using models correspond to those used in the literature; however, the authors' procedures are computationally simpler