About critical path analysis

The critical path is the route that takes the longest time to complete in a diagram and identifies which route to focus on. By identifying the activities in a critical path, you can focus your efforts on reducing their durations in order to improve the overall performance of the process. These efforts may involve examining the process model itself, or performing process instance resource allocation analysis to investigate whether costs and durations can be reduced by adjusting resource levels.

Note: For the critical path to be analyzed, durations must be specified for all activities in a given diagram. Use scenarios to modify diagrams in order to improve a process and make it more efficient before making changes to the original diagram or process map.

Principles of critical path analysis

TIBCO Nimbus®  sets the start activity on each path to a start time of zero. The Early/Late Start, Early/Late Finish and Float times are then calculated for each subsequent activity in the diagram.

Early Start (ES) - the earliest possible start time of an activity, relative to the start time of the first activity (i.e. zero).

Late Start (LS) - the latest possible start time without increasing the overall duration of the process

Early Finish (EF) - the finish based on the early start plus the activity duration

Late Finish (LF) - the finish based on the late start plus activity duration

Float - the late start minus the early start (i.e. flexibility on activity duration without increasing the overall process duration)

Example

In the diagram above, the critical path includes activities A, B, C and D. Activity E is not the route of the critical path as it takes less time (2 hours) than activity C (10 hours). Therefore there is some flexibility for activity E in terms of start times and duration, which is defined by the Float value. In this example:

Float = Duration of activity C - Duration of activity E = 8 hours

The total duration of activities A and B is 10 hours, therefore the Early Start for activities C and E is 10 hours.

The Late Start of activity E is 18 hours since it has a float of 8 hours. The Late Start of activity C must be the same as the Early Start, i.e. 10 hours, since activity C is on the critical path.

The Early Finish for activity E is 12 hours and the Late Finish is 20 hours.

As activity C is on the critical path, the Early Finish is the same as the Late Finish, i.e. 20 hours.

TIBCO Nimbus®  allows for a process map to represent a live project or situation, so you can enter Late values if, for example, an activity is running late. In the example above, activity C may be running 2 hours late. This would impact activity E by increasing its Late Start and float by 2 hours. Late values affect the total duration of the activity and therefore also the diagram cost and FTE values.