In the authors' experience, it is very important to construct a simple activity-on-node precedence diagram to portray clearly the assumed precedence relationships between the activities selected for the whichway portrayal of the project. It is also important to construct a separate but directly related Gantt chart to portray the implied timing. Modern linked bar chart software makes it tempting to combine these two traditional graphs in a single graph, but clarity and generality is lost if this is done.
At a very detailed planning level, it may seem that precedence relationships are always strict and simple, and defined by the task nature of the activities (e.g., the water must be boiled before we make the tea). At the strategic-planning level—the level most appropriate for initial risk management—precedence relationships tend to be fuzzy and complex, and defined by design and resource issues as well as the task nature of activities.
The strategic-level views of activity precedences and timing used for project risk management should capture very important alternative approaches to the project that detailed portrayals obscure. Consider Examples 5.5 and 5.6.
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