Rules Of Network Construction
1. Each defined activity is represented by one and only one arrow in the network.
2. Before an activity can be undertaken, all activities preceding it must be completed.
3. The arrows depicting various activities are indicative of logical procedure only. The length and bearing of the arrows are of no significance.
4. The arrow direction indicates the general progression in time. Head events and Tail events.
5. When some activities terminate at one event, it indicates that no activity emanating from that event may start unless all activities terminating there have been completed.
6. Events are identified by numbers.
7. The activities are identified by the numbers of their starting and ending events or by alphabets.
8. A network should have only one initial and terminal node.
9. Parallel activities between two events, without intervening events, are prohibited. When two or more parallel activities in a project have the same head and tail events, dummy activities are needed in constructing the network. Dummy activities do not consume time or resources. An efficient network contains a minimum number of dummy activities required to portray the correct precedence relationships.
10. Looping is not permitted in a network.
Procedure For Network Analysis
Consider all the paths in a project, beginning with the start event and stopping at the end event.
For each path, calculate the time of execution.
The path with the largest time is called the critical path and the activities along this path are called critical activities or bottleneck activities.