Precedence diagramming method

Sketching out an ordered network

Precedence diagramming method (PDM) is one of the tools and techniques for the PMI process to sequence activities. It is used to identify the order of the activities and their sequence in the schedule. The diagram shows which activities are dependent on, or must come after, which others. Laying out the sequence of activities may also help to identify gaps or missing activities.

There are four types of dependencies:

• finish-to-start
• finish-to-finish
• start-to-start
• start-to-finish

A PDM network is an example of an activity-on-node diagram.

Related: start and finish times, arrow diagramming method (ADM), dependencies, conditional diagramming method

Conventions

A precedence diagram has ovals for the beginning and ending of the activities. This is a zero-duration activity, also known as an "event" or "milestone". Between these are "nodes" representing the activities with one-directional arrows going between them to show the necessary direction in time or dependency.

External links

• Bright Hub Project Management on the precedence diagramming method