Improved inclusion-exclusion identities and inequalities based on a particular class of abstract tubes

Abstract

Recently, Naiman and Wynn introduced the concept of an abstract tube in order to obtain improved inclusion-exclusion identities and inequalities that involve much fewer terms than their classical counterparts. In this paper, we introduce a particular class of abstract tubes which plays an important role with respect to chromatic polynomials and network reliability. The inclusionexclusion identities and inequalities associated with this class simultaneously generalize several wellknown results such as Whitney’s broken circuit theorem, Shier’s expression for the reliability of a network as an alternating sum over chains in a semilattice and Narushima’s inclusion-exclusion identity for posets. Moreover, we show that under some restrictive assumptions a polynomial time inclusion-exclusion algorithm can be devised, which generalizes an important result of Provan and Ball on network reliability. © 1999 Applied Probability Trust.