The Precedence Diagramming Method

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One of the early methods for representing project activities as a network dates back to the early 1950s and the Polaris Missile Program. It is called the activity-on-the-arrow (AOA) method. As Figure 6.1 shows, an arrow represents each activity. The node at the left edge of the arrow is the event "begin the activity," while the node at the right edge of the arrow is the event "end the activity." Every activity is represented by this configuration. Nodes are numbered sequentially, and the sequential ordering had to be preserved, at least in the early versions. Because of the limitations of the AOA method, ghost activities had to be added to preserve network integrity. Only the simplest of dependency relationships could be used. This technique proved to be quite cumbersome as networking techniques progressed. One seldom sees this approach used today.

With the advent of the computer, the AOA method lost its appeal, and a new method replaced it. Figure 6.2 shows the activity-on-the-node (AON) method. The term more commonly used to describe this approach is precedence diagramming method (PDM).

Precedence Diagram Method Example

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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