How do Network Diagrams work?
There are two types of network diagrams: The Arrow Diagram and the Precedence diagram. The arrow diagram depicts nodes for events and arrows for activities. The precedence diagram depicts activities in the order they occur. If you work in IT you will most likely use the arrow diagram, depicted to the left.
‘A’ and ‘B’ each represents an event node. These event nodes refer to an instant when an activity is started or completed. An event node occurs only when all activities entering the node have been completed. The arrow represents the activity that takes place during the event. For example, if a task in a project were “research competition’s ad campaign," then the event nodes would designate the start and finish of this activity whereas the arrow would designate the activity itself.
Using the arrow and node method, you can depict project dependencies. In the diagram to the right, you see that Event C depends upon activities from Events A and B to be completed, and Event D depends upon Event C’s activities to be completed.
Dotted lines with arrows represent “dummy arrows." Rather than depict a dependency between two items, these arrows depict a logical relationship. Dummy arrows have no duration. They do not depict an activity. Instead, they transfer logic from one event node to another.
Once the project is mapped out, you can write a key for the visual representation, listing the duration of events and activities. The network diagram will provide you and your project team with a full visual representation of your project.