After you have identified various activities of the project and defined the sequence in which these activities should be carried out along with the due relationships existing among the activities, the next step is to draw a network diagram that is a graphical representation of the sequence you have identified for the activities. When you draw a network diagram of the project activities, you use various nodes representing various activities that are connected to each other with arrows based on the relationship you have identified among these activities.
A network diagram is one of the most common tools used in project management. Even though you have identified the sequence of activities, it does not help you to channelize your efforts until you have created a network diagram. The network diagram helps you to identify the critical path of the project. A critical path defines the sequence of project activities that add up to the longest sequence of activities that you must perform to complete the project. The critical path indicates the shortest duration that the project would take to complete it.
The entire network diagram is enclosed between two nodes indicated by the Start and End nodes. To identify the critical path of the project, you consider various project sequences of activities right from the Start node till the End node. The sequence of activities that take the longest duration is considered as the critical path of the project.
When creating a network diagram, you also mention the duration for each activity. When you add up the duration of each activity of the critical path to identify the minimum time the project would require completing it from start to end.
You can use any of the following methods and techniques to create an activity diagram for a project:
- Drawing Network Diagrams by Using the Precedence Diagramming Method: Also known as Activity on Node method, this is the most common method used to draw network diagrams across the projects. In this method, you create nodes or boxes that represent activities and connect these nodes by using arrows that show the dependency between the activities these arrows connect.
- Drawing Network Diagrams by Using the Arrow Diagramming Method: Also known as Activities on Arrows method, when you create a network diagram by using the arrow diagraming method, you use arrows to represent activities instead of nodes in the resultant network diagram.
Drawing Network Diagrams by Using the Graphical Evaluation and Review Technique (GERT) Diagramming Method: The Graphical Evaluation and Review Technique (GERT) diagramming method is a modified network diagram that enables you to create loops between the activities. You use this method when any of the project activities are recursive. For example, after designing you need to test the design. However, when a gap is identified in the testing phase, you need to revisit the design phase. You can represent such recursive relation between the design and test activities by using the GERT diagramming method.