FTRES (Fault Tree Rare Event Simulator)

Organisation:	University of Twente (THE NETHERLANDS)
Functionality:	Rare Event Simulation in Dynamic Fault Trees
Tools used:	CADP (Construction and Analysis of Distributed Processes) DFTCalc
Period:	2017
Description:	A popular method to estimate dependability is the Monte Carlo simulation of a dynamic fault tree (DFT). However, in the presence of rare events, the number of simulations required for accurate estimations grows extremely large. Thus, estimating the failure probabilities of highly reliable systems is a challenging problem. Rare event simulation techniques overcome the problem by adjusting the probabilities to make failures less rare, and subsequently calculating a correction for this adjustment. The fault tree rare event simulator (FTRES) implements such a rare event simulation technique for dynamic fault trees. FTRES is based on the representation of a DFT as an I/O-IMC (Input/Output Interactive Markov Chain). The computation of the I/O-IMC is compositional, in the sense that each element of the DFT is represented as a separate I/O-IMC, and then composed to yield the overall I/O-IMC. FTRES uses DFTCalc to compute the I/O-IMC for each element of the DFT, but computes the overall composition on the fly during the rare event simulation, using CADP to generate the LTS of each element.
Conclusions:	FTRES has been applied to several case studies. Compared to standard Monte-Carlo simulation, it yields more precise results and can handle larger examples. Compared to DFTCalc, it requires less memory, less time for large models, and can handle larger examples.
Publications:	[Ruijters-Reijsbergen-deBoer-Stoelinga-17] Enno Ruijters, Daniël Reijsbergen, Pieter-Tjerk de Boer, and Mariëlle Stoelinga. "Rare Event Simulation for Dynamic Fault Trees". Proceedings of the 36th International Conference on Computer Safety, Reliability, and Security (SAFECOMP'2017), Trento, Italy, LNCS 10488, pages 20-35, Springer Verlag, September 2017. Available on-line at: http://eprints.eemcs.utwente.nl/27862/01/SAFECOMP2017.pdf or from the CADP Web site in PDF or PostScript [Ruijters-Reijsbergen-deBoer-Stoelinga-19] Enno Ruijters, Daniël Reijsbergen, Pieter-Tjerk de Boer, and Mariëlle Stoelinga. "Rare Event Simulation for Dynamic Fault Trees". Reliability Engineering & System Safety, 2019. Available on-line at: https://doi.org/10.1016/j.ress.2019.02.004
Contact:	Enno Ruijters P.O. Box 217 7500 AE Enschede THE NETHERLANDS Tel: +31 53 489 5108 Email: e.j.j.ruijters at utwente.nl
Further remarks:	This tool, amongst others, is described on the CADP Web site: http://cadp.inria.fr/software

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