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On program testing issues in software reliability—a survey
World Abstracts on Microelectronics and Reliability We describe various failures modes for these MOS devices: --Permanent failures affecting a single memory cell a column of cells or the whole component. --Transient (soft) errors generated by alpha particles. Then we define a reliability computation method founded on the theory of MARKOV chains. Effects of failures modes and maintenance policy are included in this method. A numerical example is given: one megabyte memory using eight bytes words and 16 kbits devices. Then we mention possible extensions of this method.
On the methods of obtaining interval reliability of redundant systems. R. SUBRAMANIANand N. RAVICHANDRAN. Proc.
CNET Conference on Reliability and Maintainability, Tregastel, France, p. 219 (8-12 September 1980). In the analysis of redundant repairable systems the usual measures of system effectives are reliability and/or availability. However, there is another important measure known as the interval reliability which is more general than these two measures. While reliability and availability are concerned with the time to the first system failure and successful operation of the system at any specified time respectively, the interval reliability is concerned with the probability that the system is up in an arbitrary time interval. In this article we present some methods of obtaining the interval reliability of various types of systems.
Reliability considerations for new satellite systems. F. BEHMANN. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 208 (8-12 September 1980). New increased capability commercial satellite systems configurations are optimized for improved reliability, higher earning power and increased cycle life at minimum cost and risk. Telesat's realistic Weibull increasing failure rate models for travelling wave tubes and batteries, based on theoretical and measured data, are used to predict spacecraft reliability with high confidence. Achieved reliability of the present Telesat system correlate very well with the realistic Weibull predictions. Concepts of systems worth are used by Telesat to measure the effectiveness of new satellite systems versus the present systems. Satellite systems effectiveness of new programs is assured by the implementation of comprehensive Product Assurance requirements with emphasis on special screening, acceptance and life testing of life limiting items. On program testing issues in software reliability--a survey. INDER M. SOL Microelectron. Reliab. 20, 483 (1980). On account of various difficulties encountered with establishing the proof of correctness for software systems; the program testing seems to be the only sure way to prevent malfunctions from occurrence and thus to improve the software reliability. Whereas program is a reductive process; program testing is an affirmative process since everything done in testing can potentially contribute information about the quality of program being tested. Testing is the process of executing programs with representative input data or conditions, for which the correct results are known to determine whether incorrect results occur. This paper makes an attempt to provide a cross-section of current program testing technology--ranging from philosophical issues to research and development concepts to the extent that the known literature permits. Simulation of the system availability--a renewal theory approach. F, A. TILLMAN, R. F. NASSAR,WAY KUO and C. L. HWANG. Proc. CNET Col!ference on Reliability and Maintainability, Tregastel, France, p. 322 (8-12 September 1980). The solution to the general availability problem is difficult to obtain analytically. Thus a simulation approach is
617
presented to solve this problem by utilizing renewal theory. Instantaneous availability g(t), which is defined as "the probability that the system is operational at any time t," is solved via renewal theory by representing the system as a two-state stochastic process; the defined states are on time (To,) and offtime (Ton) which are combined to form the total cycle time (T). The instantaneous availability, g(t), is given by g(t) = [ 1 - F o n ( t ) ] +
fo
[l-Fon(t-s)]dm(s )
where Fort(' ) is the cumulative distribution of system on time, and re(s) is the expected number of renewals. The analytical solution to the above problem is quite general and can be applied to any adjusted system cycle time and on time distribution. Using this equation as our model, a numerical solution is obtained by simulation. A numerical example is presented to verify the simulation model. The example assumes a gamma distribution for Ton and T so the simulation solution using the model could be compared to the analytical solution. The results of this verification indicate that simulation slightly underestimates the analytical solution, but gradually approaches the analytical solution as the cycle time T is increased.
Program structures for reliable programming. J. P. BANATRE, B. GAMATIE and F. PLOYETTE. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 50 (8-12 September 1980). (In French). This paper discusses language structures which support the construction of reliable distributed programs. These programs are expressed in terms of cooperating processes. Two main aspects are emphasized: the possibility of intensive static type checking and the provision of exception handling mechanisms for interacting processes. PBX's self test and security. J. VUICHARD. Proc. CNET
Conference on Reliability and Maintainability, Tregastel, France, p. 247 (8-12 September 1980). (In French). This system is a multi-processors based system. Its high quality and availability level is reached by self-testing, self correcting mechanisms, automatic flip-flopping on back-up processors and messages rerouting to correct serial link problems.
Evaluation of state probability of repairable systems when maintenance policies are independent of the state of the system. P. BOYER and CH. KUBIAK. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 315 (8-12 September 1980). (In French). After having defined different states of"health" of an ESS control: available state, non-impaired state and emergency state (including outage), we propose a solution to measure these states. We mainly assume: (1) The time evolution of state probabilities of nonrepairable system is available. (2) The maintenance does not depend of the state of the control and is modelled by a renewal process of interarrival law: Erlang-p, p non-negative. We give the expressions of the state probabilities, defined as usual (conditional probabilities to the event "at the beginning the system is new"). We provide the evolution of X(t), the probability of nonimpaired state, for an ESS control. The results are then discussed. For a given realization co of the maintenance, the time evolution of the state probability F(t) is a trajectory of a stochastic process F(t, co). The previously defined probabilities are the mean values on f2 of these processes. The study of the variability of the process yields a relation between a measure of a state and a confidence level associated to this measure. We show that this confidence level depends on nothing but the maintenance process.
On the methods of obtaining interval reliability of redundant systems. R. SUBRAMANIANand N. RAVICHANDRAN. Proc.
CNET Conference on Reliability and Maintainability, Tregastel, France, p. 219 (8-12 September 1980). In the analysis of redundant repairable systems the usual measures of system effectives are reliability and/or availability. However, there is another important measure known as the interval reliability which is more general than these two measures. While reliability and availability are concerned with the time to the first system failure and successful operation of the system at any specified time respectively, the interval reliability is concerned with the probability that the system is up in an arbitrary time interval. In this article we present some methods of obtaining the interval reliability of various types of systems.
Reliability considerations for new satellite systems. F. BEHMANN. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 208 (8-12 September 1980). New increased capability commercial satellite systems configurations are optimized for improved reliability, higher earning power and increased cycle life at minimum cost and risk. Telesat's realistic Weibull increasing failure rate models for travelling wave tubes and batteries, based on theoretical and measured data, are used to predict spacecraft reliability with high confidence. Achieved reliability of the present Telesat system correlate very well with the realistic Weibull predictions. Concepts of systems worth are used by Telesat to measure the effectiveness of new satellite systems versus the present systems. Satellite systems effectiveness of new programs is assured by the implementation of comprehensive Product Assurance requirements with emphasis on special screening, acceptance and life testing of life limiting items. On program testing issues in software reliability--a survey. INDER M. SOL Microelectron. Reliab. 20, 483 (1980). On account of various difficulties encountered with establishing the proof of correctness for software systems; the program testing seems to be the only sure way to prevent malfunctions from occurrence and thus to improve the software reliability. Whereas program is a reductive process; program testing is an affirmative process since everything done in testing can potentially contribute information about the quality of program being tested. Testing is the process of executing programs with representative input data or conditions, for which the correct results are known to determine whether incorrect results occur. This paper makes an attempt to provide a cross-section of current program testing technology--ranging from philosophical issues to research and development concepts to the extent that the known literature permits. Simulation of the system availability--a renewal theory approach. F, A. TILLMAN, R. F. NASSAR,WAY KUO and C. L. HWANG. Proc. CNET Col!ference on Reliability and Maintainability, Tregastel, France, p. 322 (8-12 September 1980). The solution to the general availability problem is difficult to obtain analytically. Thus a simulation approach is
617
presented to solve this problem by utilizing renewal theory. Instantaneous availability g(t), which is defined as "the probability that the system is operational at any time t," is solved via renewal theory by representing the system as a two-state stochastic process; the defined states are on time (To,) and offtime (Ton) which are combined to form the total cycle time (T). The instantaneous availability, g(t), is given by g(t) = [ 1 - F o n ( t ) ] +
fo
[l-Fon(t-s)]dm(s )
where Fort(' ) is the cumulative distribution of system on time, and re(s) is the expected number of renewals. The analytical solution to the above problem is quite general and can be applied to any adjusted system cycle time and on time distribution. Using this equation as our model, a numerical solution is obtained by simulation. A numerical example is presented to verify the simulation model. The example assumes a gamma distribution for Ton and T so the simulation solution using the model could be compared to the analytical solution. The results of this verification indicate that simulation slightly underestimates the analytical solution, but gradually approaches the analytical solution as the cycle time T is increased.
Program structures for reliable programming. J. P. BANATRE, B. GAMATIE and F. PLOYETTE. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 50 (8-12 September 1980). (In French). This paper discusses language structures which support the construction of reliable distributed programs. These programs are expressed in terms of cooperating processes. Two main aspects are emphasized: the possibility of intensive static type checking and the provision of exception handling mechanisms for interacting processes. PBX's self test and security. J. VUICHARD. Proc. CNET
Conference on Reliability and Maintainability, Tregastel, France, p. 247 (8-12 September 1980). (In French). This system is a multi-processors based system. Its high quality and availability level is reached by self-testing, self correcting mechanisms, automatic flip-flopping on back-up processors and messages rerouting to correct serial link problems.
Evaluation of state probability of repairable systems when maintenance policies are independent of the state of the system. P. BOYER and CH. KUBIAK. Proc. CNET Conference on Reliability and Maintainability, Tregastel, France, p. 315 (8-12 September 1980). (In French). After having defined different states of"health" of an ESS control: available state, non-impaired state and emergency state (including outage), we propose a solution to measure these states. We mainly assume: (1) The time evolution of state probabilities of nonrepairable system is available. (2) The maintenance does not depend of the state of the control and is modelled by a renewal process of interarrival law: Erlang-p, p non-negative. We give the expressions of the state probabilities, defined as usual (conditional probabilities to the event "at the beginning the system is new"). We provide the evolution of X(t), the probability of nonimpaired state, for an ESS control. The results are then discussed. For a given realization co of the maintenance, the time evolution of the state probability F(t) is a trajectory of a stochastic process F(t, co). The previously defined probabilities are the mean values on f2 of these processes. The study of the variability of the process yields a relation between a measure of a state and a confidence level associated to this measure. We show that this confidence level depends on nothing but the maintenance process.