3. DESCRIPTION OF PROBLEM OR FUNCTION
IMPORTANCE computes various
measures of probabilistic importance of basic events and minimal
cut sets to a fault tree or reliability network diagram. The
minimal cut sets, the failure rates and the fault duration times
(i.e., the repair times) of all basic events contained in the
minimal cut sets are supplied as input data. The failure and
repair distributions are assumed to be exponential. IMPORTANCE, a
quantitative evaluation code, then determines the probability of
the top event and computes the importance of minimal cut sets and
basic events by a numerical ranking. Two measures are computed.
The first describes system behavior at one point in time; the
second describes sequences of failures that cause the system to
fail in time. All measures are computed assuming statistical
independence of basic events. In addition, system unavailability
and expected number of system failures are computed by the code.