Constructing the Project Network

The first step is to determine the end objective. Next, the major areas of endeavor that will contribute to the accomplishment of the plan must be determined.
The major activities that lead to the end activity are then identified and listed. After this the following procedure is adopted.

• Write the description of the end objective near the right margin of a large piece of paper, centered vertically.
• Determine which major activities must be completed just prior to the completion of the objective, and write them to the left of the last activity.
• Indicate, by drawing a line, the work to be done between the events.
• Determine which activities must be completed prior to the accomplishment of each of the activities listed and record them and their associated activities, another step to the left.
• Report the process till the first activity is reached. Layout the network so that all activity lines flow from left to right. They may cross one another as long as they can be followed easily.
• When the network has been laid out, assign even number starting with the beginning event in the order in which they must be completed.

Rules for Network Development

• No event can occur until all the activities leading into that event have been completed.
• An activity succeeding an event cannot be started until that event has occurred.
• There should not be any close loop in the network, that is, an event cannot occur more than once.
• Activity lines cannot be drawn from the middle of other activity. If it is necessary to start an activity from the middle, one must define the exact point at which the second activity starts. An event is placed at this point, and this event may initiate the desired activity.
• All activity heads should be marked with an arrow to indicate the direction of flow.
• All events should be numbered and so this number should be unique, as to give an activity reference.
• All activities should have unique reference number, i.e. between two events there should be only one activity.
• In a network, flows are from left to right, that is , activity lines with arrow heads that point to the left should be avoided.
• There should be only one initiating event and one objective event, thus every activity on the networks should be completed to reach the end objective work. Hanging activities are not permissible.

Dummy Activities

Dummy activities are activities which consume no resource or time. They are used:
i. To maintain the logic in the network diagram.
ii. To show interdependencies between events, and
iii. To give a unique number or activity reference to an activity.
Dummies are also often used to tie the completion of several activities to the beginning of a single activity or vice versa.

Topological Ordering

The activities of the project are ordered in such a manner that no activity appears in the list before all its predecessor activities have been considered. Hence activities are ordered according to the lower preceding node number first.