Key CPM Scheduling Terms
CPM scheduling is a very important scheduling technique in project management. There are a number of key terms used in CPM scheduling. If you do not understand all these terms, then it would be difficult for you to get to know different aspects of CPM scheduling.
Critical Path Method
The Critical Path Method (CPM) is a network of events, each one of them are linked to following activities and this model helps to understand how a project can be performed.
Task or Activity
Task or Activity is a portion of a project which needs time and/or resources to finish and which has a definite start and finish time.
Predecessor is an activity that occurs before another activity and is related to its successor. A predecessor activity controls the start or finish date of its successor.
Successor is an activity that occurs after another activity and is related to its predecessor.
Early Dates are the earliest time an activity can take place.
Late Dates are the latest time an activity can take place.
Float or Slack
Float or Slack is the amount of time an activity can be delayed without affecting the finish date of the project.
Free Float is the amount of time an activity can be delayed without affecting the float of another activity. Free float can never be less than zero.
Total Float is the total number of planning units an activity can be delayed without affecting the project completion.
Update is the process of revising activity data to incorporate actual progress.
Critical activity is an activity with zero or negative float.
Critical path is the path from start activity through finish activity in the schedule with least amount of float.
Longest Path is the chain of continuous activities that requires the greatest amount of time to accomplish. Longest path is often referred to as the critical path.
Relationship is a logical tie between two or more activities. There are four types of relationships: Finish-To-Start, Finish-To-Finish, Start-To-Start and Start-To-Finish.
Lag is a delay from an activity to its successor and it can be positive or negative.
Constraint is a restriction imposed on an activity or its float.
Loop is a set of activities arranged by improper logic so that the chain has no start or end date.
Organizational Breakdown Structure
Organizational Breakdown Structure (OBS) is used to group tasks by responsible organization or discipline.
Work Breakdown Structure
Work Breakdown Structure (WBS) is used to group tasks by a work area. A work area can be a project phase, a system module or even a physical area.
Arrow Diagramming Method
Arrow diagramming method is a graphical technique to represent a network. Different activities are represented on arrows. The tail of the arrow shows the start of activity and the arrow head depicts the work completion. The description is written on the shaft of the arrow.
Precedence Diagramming Method
Precedence diagramming method is a graphical technique to represent a network. Different activities are represented on nodes. The activity description is written in a box and connecting lines have arrow heads showing direction.