In the activity-on-arrownetwork, there are essential differences between positive activity and dummy activity.
双代号网络图中，虚工作和实工作有着本质的区别，其主要作用是传递工作之间的逻辑关系。
2
With the demonstration and comparison of activity-on-arrownetwork and time-scaled network in this paper, proper conclusion is expected to drawn.
文章通过对双代号网络、单代号网络及时标网络的对照及论证，得出虚工作的时间参数可以不计算的结论。
3
In view of activity-on-arrownetwork drawing difficultly, describes the methods of determine the dummy arrow. It will enable the rapid and accurate drawing.