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Most projects, whether big or small, are undertaken either to create a new structure, such as a plant, an airport, an Olympic stadium, a bridge, a new product, etc., or to modify an existing structure, such as a plant expansion, adding a new production line, expanding a highway, etc. In most cases, the late completion of the project, such as finishing the Olympic stadium two weeks after the opening of the Olympics, or having a new airports' opening delayed until after the elections, etc., generally carries with it some significant negative ramifications for the project owner. At the same time, there are many cases where the early completion of the project will provide the project owner with significant positive ramifications, such as the market share gained by preempting the competitions' launching of a new product, or the increase in sales achieved by bringing the plants productive capabilities on-line sooner, etc.
Another important characteristic of most projects is that many of the resources performing the individual project tasks are sub-contracted resources, at least in terms of their relationship to the project manager. As sub-contracted resources, they are often committed to completing more than one project specific task during any given window of time. The issue of resource availability is often further complicated by the nature of the disturbances associated with most project specific tasks. As a result, most sub-contractors will only commit to completing a project specific task within a window of time and by a specific date, regardless of the fact, that the actual time required to complete the project specific task is generally much smaller than the allotted time window. Hence, the detail scheduling of the sub-contractors resources is generally something that most project managers have little or no direct control over.
Lastly, most projects usually involve the