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