Network Diagrams are a graphical portrayal of the activities and events of a project. They show how each activity relates to others in the project, the sequence of activities, and the need to perform some tasks before others. Networks also facilitate the determination of the impact of early or late starts or finishes, provide information about the allocation of resources, and allow managers to do “what if” analyses. With this information, managers may view the status of the plan, analyze progress, and evaluate alternatives.
Definition: A project network diagram is a visualization that shows the activities, duration, and interdependencies of tasks within a project.
Figure: Arrow Diagramming Method Network Diagram
Types of Network Diagrams
There are two types of network diagrams that are used:
- Arrow Diagramming Method (ADM), also called “activity network diagram” or “activity on arrow”
- Precedence Diagramming Method (PDM), also called “node network” or “activity on node.”
Benefits of a Network Diagram
There are a number of benefits that program personnel can have utilizing a network diagram. A few benefits are:
- The project manager can track each element of a project and share status.
- Report progress to stakeholders
- Establishing project workflows
- Tracking dependencies
- Display any bottlenecks that pose a risk
Network Diagram Requirements
The following conditions must exist to develop a Network Diagram:
- All program activities must be clearly defined, including identifiable start and completion points.
- A logic diagram showing the sequence and interrelationships of activities must be developed.
- The time to complete each activity must be estimated as accurately as possible.
Network Diagram Tools
A number of tools and techniques are useful in developing a network and logic diagram that reflects the desired activity sequencing. They include various network scheduling techniques that can be used to include: 
- Critical Chain Method (CCM)
- Critical Path Method (CPM)
- Precedence Diagram Method (PDM)
- Program Evaluation and Review Technique (PERT)
Network Diagram Development
Accomplishing these things may require considerable effort and the involvement of people familiar with the overall project and those responsible for executing various groups of activities. This up-front effort provides an understanding of project requirements and early identification of potential problem areas. The eventual network diagram is usually developed into a Gantt Chart.
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