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
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
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.