Precedence diagram method explained

The precedence diagram method (PDM) is a tool for scheduling activities in a project plan. It is a method of constructing a project schedule network diagram that uses boxes, referred to as nodes, to represent activities and connects them with arrows that show the dependencies. It is also called the activity-on-node (AON) method.

• Critical tasks, noncritical tasks, and slack time
• Shows the relationship of the tasks to each other
• Allows for what-if, worst-case, best-case and most likely scenario

Key elements include determining predecessors and defining attributes such as

• early start date
• late start date
• early finish date
• late finish date
• duration
• activity name
• WBS reference

Slack/Float: Determines the duration of activity delay that the project can tolerate before the project comes in late. The difference between the earliest and the latest start time. i.e. Slack = latest start date - earliest start day or Slack = latest finish time - earliest finish time.

Any activities which have a slack of 0, they are on the critical path.

Different Precedence diagram Methods

• Arrow diagramming method
• Project network
• Critical-path method
• Gantt chart
• Program evaluation and review technique

Further reading

• Book: Kerzner, Harold . 2009 . Project Management: A Systems Approach to Planning, Scheduling, and Controlling . 10th . Wiley . 978-0-470-27870-3. Harold Kerzner .
• Book: Sanghera, Paul . 2019. PMP in Depth . Third . Apress . 978-1-4842-3910-0 . 10.1007/978-1-4842-3910-0 . en-US.

External links

• Precedence Diagram Method at Better Projects