Probability of Failure on Demand – The Why and the How

We study the reliability analysis of fire sprinkler systems. We show that the characteristic features of Dugan's dynamic fault trees (DFTs) such as spare management, temporal ordering of failures and functional dependencies, are natural and adequate mechanisms to model various relevant phenomena in realistic fire sprinklers. For DFT analysis, we employ probabilistic model checking, an automated technique to assess reliability along with correctness. This is to date the most scalable, numerical DFT analysis technique. We show how standard reliability measures of fire sprinkler systems can be efficiently computed using the STORM model checker. In addition, we consider metrics beyond standard reliability, e.g., the probability to fail without going through a degradation phase and the worstcase reliability achieved after degradation. We illustrate our approach by fire sprinkler systems in shopping centers.

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“…IEC-61508 recommends PFH (PFD avg ) computation for high-(low-) demand modes of operation. As discussed by [15],…”

Section: B Case Study: Fire Suppression In Shopping Centersmentioning

confidence: 94%

Modelling and Analysis of Fire Sprinklers by Verifying Dynamic Fault Trees

Khan

Katoen

Volk

et al. 2021

2021 10th Latin-American Symposium on Dependable Computing (LADC)

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“…For example, logging systems in networked environments may become temporary unavailable and unable to record actions happening in the network (Basin et al, 2012). The reliability of a resource is usually modelled by the probability of failure (Braband, Vom Hövel, & Schäbe, 2009); i.e., likelihood that a piece of equipment will fail at a given time.…”

Section: Appendix C Resource Failurementioning

confidence: 99%

Resource-bounded Norm Monitoring In Multi-agent Systems

Criado

2018

jair

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Norms allow system designers to specify the desired behaviour of a sociotechnical system. In this way, norms regulate what the social and technical agents in a sociotechnical system should (not) do. In this context, a vitally important question is the development of mechanisms for monitoring whether these agents comply with norms. Proposals on norm monitoring often assume that monitoring has no costs and/or that monitors have unlimited resources to observe the environment and the actions performed by agents. In this paper, we challenge this assumption and propose the first practical resource-bounded norm monitor. Our monitor is capable of selecting the resources to be deployed and use them to check norm compliance with incomplete information about the actions performed and the state of the world. We formally demonstrate the correctness and soundness of our norm monitor and study its complexity. We also demonstrate in randomised simulations and benchmark experiments that our monitor can select monitored resources effectively and efficiently, detecting more norm violations and fulfilments than other tractable optimization approaches and obtaining slightly worse results than intractable optimal approaches.

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“…One should, however, remind that (8) is not easily applicable to analog computers. Some more detailed considerations of the here discussed problems have been published from other points of view, without considering confidence limits, however [14,27].…”

Section: Software Working Continuouslymentioning

confidence: 99%

Statistical Considerations on Software-Safety Estimation in Licensing

Ehrenberger¹

2018

MCS

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During the discussions in preparation of the new versions of the International Electrotechnical Commission (IEC) standards IEC 61508-3 and IEC 61508-7, controversies regarding the proper roles of statistical validation or verification of safety-related software have emerged. These controversies regard changing demand profiles and continuous operation versus on-demand operation. This contribution derives a formula for calculating the failure probability per demand of software that has been tested under a demand profile that is different from the profile of its intended use. It also explains how failure rates can be expressed in terms of failure probabilities per demand, if the operational conditions are known. It further describes how software that is alternately operated continuously and on demand can be characterized in statistical terms and how the two operation modes can be recognized during a statistical evaluation. The notion of "mission" is suggested for sequences of demands or mixtures of demand-driven and continuous operation of software. In order to allow statistical calculations many requirements have to be met strictly. They are listed in the appendix. This article can hopefully facilitate licensing of software in many cases. Remarks are invited.

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Probability of Failure on Demand – The Why and the How

Cited by 14 publications

References 2 publications

Modelling and Analysis of Fire Sprinklers by Verifying Dynamic Fault Trees

Modelling and Analysis of Fire Sprinklers by Verifying Dynamic Fault Trees

Resource-bounded Norm Monitoring In Multi-agent Systems

Statistical Considerations on Software-Safety Estimation in Licensing

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