CPM AND PERT
CPM (Critical Path Method) and PERT (Program Evaluation and Review Technique) are network-based methods designed to assist in the planning, scheduling, and comrol of projects. A project is defined as a collection of interrelated activities with each activity
consuming time and resources. The objective of CPM and PERT is to provide analytic means for scheduling the activities. Figure 6.38 summarizes the steps of the techniques. First, we define the activities of the project, their precedence relationships, and their time requirements. Next, the precedence relationships among the activities are repre-sented by a network. TIle third step involves specific computations to develop the time schedule for the project. During the actual execution of the project things may not pro-ceed as planned, as some of the activities may be expedited or delayed. When this hap-pens, the schedule must be revised to reflect the realities on the ground. This is the reason for including a feedback loop between the time schedule phase and the net-work phase, as shown in Figure 6.38.
The two techniques, CPM and PERT, which were developed independently, dif-fer in that CPM assumes deterministic activity durations and PERT assumes proba-bilistic durations. This presentation will start with CPM and then proceed with the details of PERT.