The problem is to schedule the construction of a five-segment bridge. To our knowledge, this problem was first published in Germany in a Ph.D. thesis at the University of Passau, and it is very commonly used as a benchmark in the constraint programming community. In this chapter, we offer a simple, efficient program for solving the problem.

The bridge is made of five segments. Five preformed bearers (or horizontal beams) must be placed on top of six vertical pillars: one bearer between any two successive pillars. In the notation generally used for this problem, the activity which consists of putting bearer number k on top of pillars number k and k+1 is denoted Tk, and we'll follow the same convention, respecting the usual naming conventions in this widely used benchmark.

Constructing each pillar means that four activities must be completed: excavation (denoted Ak for pillar number k), formwork (Sk), concrete foundation (Bk), and masonry (Mk). In addition:

The following table lists the activities to be scheduled, the duration in days for each, and the unary resource to be used (if any is necessary).