Maintainability and System Effectiveness

The process of “doing something” is known as the maintenance process. It can be viewed as the flow of maintenance tasks selected and performed by the user to retain or restore the functionality of the system during its operational process. Hence, successful completion of a maintenance task will cause the transition of the system to the SoFu. Experience teaches us that during the life of a system there will be many “failure” and “repair” events. Hence, from the point of view of “satisfying perceived needs” any engineering during its operational life will be fluctuating between SoFu and SoFa until its retirement is shown in Figure 21.1. The established pattern is termed the functionability profile because it maps states of the system during its operational life (Knezevic, 1996). Usually calendar time is used as the unit of operational time against which the profile is plotted.