EMS 1.0 Primer - Work Breakdown Structures

Status

This is a Working Draft.

Introduction

The Work breakdown structure (WBS) is a widely used tool for describing projects. While other sections of this Primer have described the interactions between EMS 1.0 service consumers and providers within a single phase of the estimation lifecycle, this section describes on the interactions involving WBS across several phases.

A WBS is a decomposition of the total work to be performed on a project into smaller units that can be estimated, assigned, measured, and tracked. A WBS should describe all the work and only the work that is to be performed on the project. The WBS therefore defines the project's scope of work.

The decomposition of work forms a tree that may have any number of levels. Each node in the tree is called a WBS element. The root node of the tree presents the project itself. Each leaf of the tree is called a terminal WBS element or work package. The work performed in any non-terminal WBS element is the sum of the work performed in all its children. The total amount of work performed in a project is the sum of that performed in all the ternimal WBS elements.

At the start of a project the WBS tree may have only a few levels, perhaps only three. The terminal WBS elements may get decomposed further as the project progresses. In practice, the decomposition stops when the WBS element produces a measureable result that can be assigned to one or a small team of people and can be completed in a few weeks or less. The WBS should focus on measureable results produced by the work and not on how the result is achieved.

Overview

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