6.3 VVT TIME AND RISK MODELING
At the individual level, VVT time modeling mirrors VVT cost modeling. Therefore, we do not repeat the entire previously provided derivation. This section will however describe the unique features of VVT modeling related to the time domain. Specifically, it extends the VVT methodology elaborated before in order to perform estimation of the time required to carry out system VVT processes.
6.3.1 System/VVT Network
The basic issue of planning and estimating the duration of projects is well established and in common use. For example, the Critical Path Method (CPM) and the Program Evaluation and Review Technique (PERT) were developed in the late 1950s by DuPont and Remington Rand in order to manage plant maintenance and by Lockheed for the Polaris Missile program (Grant, 1983). We will cite a few relevant project-scheduling definitions and then expand our discussion to cover the system/VVT lifecycle domain.
Project Scheduling Definitions
Among various definitions, we have chosen the following relevant ones:
1. A project is an interrelated set of activities that has definite starting and ending points and results in unique products or services.
2. Project duration is the elapsed time from the project start date through the project finish date.
3. A project network diagram is a schematic display of the logical precedence relationships of project activities. It is drawn from left to right to reflect project chronology.
4. An Activity-On-Node (AON) network ...