Precedence Diagramming Method (PDM)

PDM is a method of defining sequence of activities and creating schedule network diagram.PDM typically uses rectangle boxes represent activities and arrows to represent their dependencies. These boxes are called Nodes and this technique is activity on-node (AON).

PDM includes four types of dependency relationships:

Finish-to-Start: The start of the successor activity depends upon the completion of the predecessor activity.

Finish-to-Finish: The completion of the successor activity depends upon the completion of the predecessor activity.

Start-to-Start: The start of the successor activity depends upon the start of the predecessor activity.

Start-to-Finish: The start of the successor activity depends upon the completion of the start predecessor activity.

In PDM,finish-to-start is the most commonly used type of precedence relationships.

Arrow Diagramming Method (ADM)

ADM is a method of defining a project schedule network diagram that uses arrows to represent activities and connecting nodes represent their dependencies. It uses only finish-to-start dependencies and may require the dummy logical relationship.

Schedule Network Templates

Standardized project schedule network diagram templates can be used to expedite the preparation of networks of schedule activities. They can include an entire project or only a portion of it. Portions of a project schedule network diagram are often referred to as a sub-network or a fragment network.

Dependency Determination

Three type of dependence are used to define the sequence among the activities. Those are Mandatory, Discretionary or external. The project management team determines that relationships between the activities are mandatory, discretionary or external.

Mandatory Dependencies: Mandatory dependencies are inherent in the nature of the                                      project work. This is also known as hard Logic.

Discretionary dependencies: Discretionary dependencies are usually defined based on knowledge of best practices and standard procedures for the specific application area. These relationship are also called soft logic or preferential logic.

External dependencies: External dependencies involve a relationship between project activities and non-project activities .

Applying Leads and lags

A lead allows an earlier start of the activity. This helps in fast tracking in finish-to-start relationships; wherein successor activity starts before the completion of predecessor activity.

A lead creates delay in the successor activity. In finish-to-start relationship, the successor does not immediately at completion of predecessor activity.