A Resource Breakdown Structure (RBS) is a Project Document utilized by project managers. It is one of the documents created by the fourth-edition PMBOK®’s Estimate Activity Resources process.
A RBS is a heirarchical structure of a project’s resources by category and type, including human resources. This provides an illustration of the overall materials, people, equipment, and supplies needed, in addition to the quantity needed of each. The portion including people can be utilized in the Develop Human Resource Plan process. The Activity List, Activity Attributes, and Resource Calendars are used to form a starting point for estimating the needed resources. Someone with expertise can estimate how much resources are needed for a given activity, and Published Estimating Data may also be available. These estimated resources are then organized in a hierarchy. For example, Katy needs 500 cookies baked in a single day. Her RBS may include the major categories of ingredients, cooks, baking equipment, and baking tools. Her category of ingredients might be broken down into refrigerated and non-refrigerated ingredients, and the non-refrigerated ingredients category could contain 20 lbs of flour, 20 lbs of sugar, 10 cups of cocoa, and 1 cup of baking powder. Also see the earlier posting of Estimate Activity Resources Process (posted March 6, 2009).