Precedence diagram method

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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.[1]: 502 [2]: 183  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.

solving the PDM, with: BS is an early start date. BM is a late start date. KS is an early finish date. KM is a late finish date.

Different Precedence diagram Methods


  1. ^ Kerzner 2009.
  2. ^ Sanghera 2019.

Further reading[edit]

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

External links[edit]