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Safety Analysis – A quick introduction. RTS February 2006 Anders P. Ravn Aalborg University. Safety Assessment. Find faults that may lead to mishaps, analyze their relations , and estimate their consequences. May involve probabilistic reasoning (Reliability Engineering).
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Safety Analysis – A quick introduction RTS February 2006 Anders P. Ravn Aalborg University
Safety Assessment Find faults that may lead to mishaps, analyze their relations, and estimate their consequences. May involve probabilistic reasoning (Reliability Engineering).
Primary Events: Basic event – fault in atomic component Undeveloped Event – fault in composite component (may be analyzed later) External event – expected event from environment Intermediate event: Nodes inside a fault-tree Fault Tree - Events
... ... Fault Tree - Gates condition Inhibit gate
Example – ”Wake too late” Wake too late ”Inner clock” fails Phone fails Alarm clock fails
Example ”Alarm clock fails” Alarm clock fails Power fails Beeper fails electronics fail Button fails SW fails Beeper not set Button read fails
Cut Set A cut set is a set of events that causes a top level event A singleton cut set is a single point of failure
Example – ”Wake too late” Wake too late ”Inner clock” fails Phone fails Alarm clock fails
Example ”Alarm clock fails” Alarm clock fails Power fails Beeper fails electronics fail Button fails SW fails Beeper not set Button read fails
Extensions etc. • Probabilities on edges • Event tree (forward analysis from initiating event) • Combinations (cause-consequence diagrams) • Many tools Kirsten M. Hansen, Anders P. Ravn and Victoria Stavridou, From Safety Analysis to Formal Specification, IEEE Trans. Softw. Eng.24,pp. 573-584, July 1998