A project involves a collection of activities that must be performed to accomplish some goal. An example might involve the construction of a building. A builder has the task of constructing a building to meet the specifications of a design provided by an architect. The builder identifies a set of activities that must be formed to accomplish this goal such as clear the land, lay access roads, pour the foundation, erect the walls and so on. Each of the activities requires time, money and resources. Often there are precedence relations that require that before some activity may begin, others must already be completed. For example, the erection of the walls cannot begin before the foundation is ready.

Before the project begins, the builder needs to schedule the activities involved. Some purposes of a schedule are to:

• predict when the project will be completed
• predict when a subcontract should be let to perform an activity
• determine when limited resources should be obtained
• predict the cash flow over time for project expenditures and revenues.

After the project begins, it is necessary to track the performance of the various activities to assure that the project is on schedule and on budget. Some activities may require more time than originally estimated, while others may require less. Resources thought to be available may be delayed. Any change from projected values might require new schedules to be prepared or corrective actions to be taken.

These and many other considerations comprise the subject of project management. There is a great deal of literature on the subject. The book Project Management by Shtub, Bard and Globerson, 2nd edition, published by Pearson, Prentice Hall in 2005, surveys some of these considerations. The book Critical Chain by Eliyahu M. Goldratt, published by North River Press in 1997, provides a practical critique on the Project Management methods with special attention to the misleading assumptions used by traditional analysis.

One aspect of the project management problem that is the subject of quantitative analysis is project scheduling using network models and critical path methods. This section provides some of the theory associated with this aspect. It supports the Project Management Add-in described elsewhere on this site. The add-in builds the activity-on-node model and performs a variety of operations on the model including scheduling considering limited resources and project cash flows. The add-in and Excel demonstration workbooks may be downloaded from the Excel Download page.