Integer Models

Abstract

The examples on “network design” (p. 15), “river and flood models” (p. 20) and “urban water systems” (p. 21) lead us to consider networks. A useful way to describe a network is to define for each pair of nodes a function whose value is 1 if there is a direct connection between these nodes in the network, and 0 otherwise. More generally, x = 1 can be used to indicate that a certain event occurs and x = 0 that it does not. Indeed, binary (i.e., 0-1-valued) variables appear in many models, and so do also other integer-valued variables. In this chapter we shall take a look at such models.