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osate / osate2

Open Source AADL2 Tool Environment
http://osate.org
Eclipse Public License 2.0
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FTA uses probability calculation of AND for Priority AND #1971

Open reteprelief opened 5 years ago

reteprelief commented 5 years ago

See TODO comment in public static BigDecimal getSubeventProbabilities(Event event)

in FaultTreeUtil. AND (aka ALL) does a product.

Priority AND is a conditional probability P(A|B) e.g., used when modeling standby redundancy, where A has to fail and then B only after A fails.

reteprelief commented 5 years ago

Example: We generate Priority AND in the fault tree if the component has a degraded error state from which it propagates incoming errors. They are only propagated when in degraded and not when in fully operational. The component may transition into degraded due to an internal failure.

reteprelief commented 5 years ago

Here is an example of a redundant system with a primary component (ACC) and a backup component (Pilot) and Flight Surface with the logic of figuring out whose output to use - by tracking it with error states. AircraftSafetyExample3.txt acemlib.txt

jjhugues commented 5 years ago

A general description of the standby situation is at https://www.itl.nist.gov/div898/handbook/apr/section1/apr185.htm