Precedence Diagram Method (PDM)
The Precedence Diagram Method (PDM) is a project management technique used to visualize activities and their interdependencies. It is also known as the Activity on Node (AON) method, as activities are represented by nodes, and dependencies are represented by arrows connecting the nodes.
The PDM is used in the planning and scheduling phase of project management. It allows project managers to create a visual representation of the project, which helps them to identify the critical path and to estimate the duration of the project.
The components of a PDM include nodes, which represent activities, and arrows, which represent dependencies. The nodes are labeled with the activity name and the estimated duration. The arrows represent the dependencies between activities and are labeled with the type of dependency (start-to-start, start-to-finish, finish-to-start, or finish-to-finish).
The PDM is important because it helps project managers to identify the critical path, which is the sequence of activities that determines the shortest duration for the project. By identifying the critical path, project managers can focus their attention on those activities that are most important for the success of the project.
The history of the PDM can be traced back to the 1950s and 1960s, when project managers began to use network diagrams to plan and schedule projects. The PDM was developed as a refinement of these network diagrams, and it became popular in the 1970s and 1980s.
The benefits of using the PDM include better visualization of project activities and dependencies, more accurate estimation of project duration, and better identification of the critical path. However, the PDM can be complex to create and maintain, and it may not be suitable for all types of projects.
An example of a PDM can be seen in a construction project. The nodes represent activities such as excavation, foundation pouring, framing, electrical installation, plumbing installation, and roofing. The arrows represent the dependencies between these activities, such as the requirement that the excavation must be completed before the foundation can be poured. By analyzing the PDM, the project manager can identify the critical path and estimate the duration of the project.