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{\bf Klaus Dohmen}
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{\bf Inclusion-Exclusion and Network Reliability}
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Based on a recent improvement of the inclusion-exclusion principle,
we present a new approach to network reliability problems.
In particular, we give a new proof of a result of Shier,
which expresses the reliability of a network as an alternating
sum over chains in a semilattice, and a new proof of a result
of Provan and Ball, which provides an algorithm for computing
network reliability in pseudopolynomial time. Moreover, some
results on $k$-out-of-$n$ systems are established.
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