Towards the end of the fifties methods for planning, scheduling, and control of proj ects were developed on the basis that the evolution of a project can be associated with a special weighted directed graph, called activity network. In this association, the individual activities of the project correspond to the arcs, the so-called proj ect events (beginning or termination of activities) correspond to the nodes, and the durations of the activities correspond to the weights of the respective arcs of the directed graph. 1) Contiguous arcs are assigned to activities which succeed one another...