Meredith and Mantel (2000, 302) state that a schedule is the conversion of a project action plan into an operating timetable. As such, it serves as the basis for monitoring and controlling project activity and taken together with the plan and budget, is probably the major tool for the management of project. In a project environment, the scheduling function is more important than it would be in an ongoing operation because projects lack the continuity of day-to-day operations and often present much more complex problems of coordination.
Shtub, Bard and Globerson (2005, 457) identify that resources scheduling is the process by which the project manager decides which resources to obtain, from which sources, when to obtain them, how to use them and when and how to release them. Given the finite nature of resource availability, a project plan may have to be modified so that it is practical. This is the major thrust of resource planning and management.
According to Gray and Larson (2005, chapter 8), there are four major stages of the resource scheduling process. These stages are resource definition, resource allocation, resource aggregation, and resource leveling. Resource definition involves identifying the critical resources that need to be planned and managed for the successful completion of the project. In a multi-project environment as projects are competing for scarce resources, resource allocation addresses the problem of the optimum use and timing of the assignment of these resources to the various project activities. Resource aggregation involves determining the aggregate resources that will be needed, period by period, to complete all project activities. Having identified the necessary resource requirements, the last stage in the process is resource leveling, aims to ensure that the demand for resources does not exceed availability. Specifically, demand for resources is