一个复杂的工程通常可以分解成一组小任务的集合，完成这些小任务意味着整个工程的完成。例如，汽车装配工程可分解为以下任务：将底盘放上装配线，装轴，将座位装在底盘上，上漆，装刹车，装门等等。任务之间具有先后关系，例如在装轴之前必须先将底板放上装配线。任务的先后顺序可用有向图表示——称为顶点活动（ Activity On Vertex, AOV）网络。有向图的顶点代表任务，有向边(i, j) 表示先后关系：任务j 开始前任务i 必须完成。图1 - 4显示了六个任务的工程，边（ 1 , 4）表示任务1在任务4开始前完成，同样边（ 4 , 6）表示任务4在任务6开始前完成，边（1 , 4）与（4 , 6）合起来可知任务1在任务6开始前完成，即前后关系是传递的。由此可知，边（1 , 4）是多余的，因为边（1 , 3）和（3 , 4）已暗示了这种关系。-a complex project can usually be divided into a group of small tasks set to complete these tasks means that the completion of the whole project. For example, car assembly projects can be divided into the following tasks : to the chassis via the assembly line, armored axis of the seat is installed in the chassis, painting and installing the brakes, armored doors, etc.. Between tasks has, for example, installed in the shaft bottom before they must first be placed on an assembly line. The task order is available to the map -- known as the vertex (Activity On Vertex, AOV) network. A plan to the apex representative tasks, to the edge (i, j) has said : j task before i task must be completed. Figure 1 - 4 6 shows the mandate of the project, while (1, 4) a mandate in the mission completed before t