Overview
1) Overview – The continued discussion of project implementation by covering various scheduling techniques.
2) Background – Per the text, “A schedule is the conversion of a project action plan into an operating timetable.” A schedule is important because each project is unique in its own way. The basic process is to identify all tasks and sequential relationships between them, that is, which tasks must precede or succeed others. There are a number of benefits to the creation and use of these networks. Some of them are as follows:
a) It is a consistent framework for planning, scheduling, and controlling the project.
b) It can be used to determine a start and end date for every project task.
c) It identifies so-called critical activities that, if delayed will delay the project completion.
3) Network Techniques: PERT (ADM) and CPM (PDM) – PERT and CPM are the most commonly used approaches to project scheduling. Both were introduced in the 1950s. PERT has been primarily associated with R&D projects, while CPM with construction projects. Today PERT is not used much since project management software generates CPM style networks. The primary difference between them is that PERT uses probabilistic techniques to determine task durations, while CPM relies on a single duration estimate for each task. Both techniques identify the critical path (tasks that cannot be delayed without delaying the project) and associated float or slack in the schedule. In 2005 the Project Management Institute (PMI) deemed it necessary to change the names of these techniques. According to PMI, PERT is called ADM/PERT (Arrow Diagram Method) and CPM is PDM/CPM (Precedence Diagramming Method).
a) Terminology – Following are the key terms associated with the development and use of networks:
i) Activity – A specific task or set of tasks that have a start and end, and consume resources.
ii) Event – The result of completing one or more activities. Events don’t use resources.
iii) Network – The arrangement of all activities and events in their logical sequence represented by arcs and nodes.
iv) Path – The series of connected activities between any two events in a network.
v) Critical – Activities, events or paths which, if delayed, will delay the completion of the project.
To construct a network the predecessors and successors of each activity must be identified. Activities that start the network will have no predecessor. Activities that end the network will have no successor. Regardless of the technique used, it is a good practice to link the activities with no other predecessor to a START milestone. Those without any successor should be linked to an END milestone. PDM/CPM networks identify the activities as nodes in the network, called the Activity on Node (AON) network. The arrows in between the nodes depict the predecessor/successor relationships among the activities. The ADM/PERT method, on the other hand, uses Activity on Arrow (AOA) networks. Here the nodes represent .