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Project Management: Work Breakdown Structure
By Larry Gunter

What is the differences between a WBS and a project network?

Work Breakdown Structure (WBS) is the final outline, made up of subdivided work tasks that form a map of a project. The project manager uses this tool to identify all the project elements and any subsets that need to be considered in completing a project (Gray & Larson, 2008, p. 97).

A project network is different in that it is only timed activities developed from the WBS. It is a diagram that shows sequential order of completion and the relationship of tasks and the interdependencies to track the sequential order of timed activities of the project. The two approaches which are unique to a project network are activity-on-node(AON) and activity-on-arrow(AOA). These approaches have been incorporated into project management software used commonly today (Gray & Larson, 2008, pp. 146-149).

How are the WBS and project networks are linked?

The link between the WBS and the project network is in the work packages (Gray & Larson, 2008, p. 146). The project network goes beyond the WBS by identifying task dependencies, sequence of events and length of time for each activity. The project network uses the work packages from the WBS to identify the timing for the activities.

When is a hammock activity and when it is used?

Hammock activities are timed events that span a portion of the project. These activities are determined after the project network plan is determined (Gray & Larson, 2008, p. 169). Hammock activities are usually permanent resources or reoccurring costs over a segment of the project. It is used to show the total span of the cost during the project from the point where it is first used to the last time it is used. It allows project reviewers to see the activity without having to review the deeper details. It is forwarded to the total cost of the project and does not impact other activities around it (Gray & Larson, 2008, p. 170).


Gray, C., & Larson, E. (2008). BUS 517: Project management, The managerial process: 2009 custom edition (4th Edition ed.). Boston, MA: McGraw-Hill.

Larry Gunter, MBA is a Training Development Consultant at Verizon Wireless. You can read more from Larry on his blog, and you can contact him via his LinkedIn profile.

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