Knowledge Highlights

Learning Outcomes

• Define an activity
• Describe the transition from scope to schedule
• Explain the Precedence Diagramming Method(PDM)
• Distinguish the difference between a mandatory and discretionary dependency
• Define lags and leads

Define and Sequence Activities Definitions

An activity represents the effort needed to complete a work package.

Define Activities is the process of identifying and documenting the specific actions to be performed to produce the project deliverables.

It is at this point, that we can transition from the project scope—the high-level breakdown of work to be performed—to defining and planning the smaller, more manageable, schedule activities.

Sequence Activities is the process of identifying and documenting relationships among the project activities.

Precedence Diagramming Method

Precedence Diagramming Method (PDM) is a technique in which activities are linked, by one or more logical relationship, to show the sequence in which activities are to be performed.

PDM uses four types of dependencies or logical predecessor-successor relationships:

• Finish-to-Start (FS): Activity A must finish before B can start
• Start-to-Start (SS): Activity A must start before B can start
• Finish-to-Finish (FF): Activity A must finish before B can finish
• Start-to-Finish (SF): Activity A must start before B can finish

Mandatory and Discretionary Dependencies

Mandatory dependencies are either legally or contractually required, or simply a necessary part of the work.

Discretionary dependencies are when you have one resource doing several activities not because it has to be done in that order, but because you choose to do it in that order.

It is important to be able to distinguish the mandatory dependencies from the discretionary dependencies, because the discretionary ones can be changed. You usually can’t change mandatory dependencies.

Lags and Leads

Lags and leads are ways to put time between two activities in order to accurately define the logical relationship.

Lags are the amount of time a successor activity will be delayed with respect to a predecessor activity, resulting in added or positive time.

Leads are the amount of time a successor activity can be advanced with respect to a predecessor activity, resulting in subtracted or negative time (negative lags).