  A semicoherent system can be described by its structure function or,
equivalently, by a lattice polynomial function expressing the system lifetime
in terms of the component lifetimes. In this paper we point out the parallelism
between the two descriptions and use the natural connection of lattice
polynomial functions and relevant random events to collect exact formulas for
the system reliability. We also discuss the equivalence between calculating the
reliability of semicoherent systems and calculating the distribution function
of a lattice polynomial function of random variables.
