Establish a top-level work breakdown structure (WBS) to estimate the scope of the work.


The WBS evolves with the work. A top-level WBS can serve to structure initial estimating. The development of a WBS divides the overall work into an interconnected set of manageable components.

Typically, the WBS is a product, work product, or task-oriented structure that provides a scheme for identifying and organizing the logical units of work to be managed, which are called “work packages.” The WBS provides a reference and organizational mechanism for assigning effort, schedule, and responsibility and is used as the underlying framework to plan, organize, and control the work.

The activities in a WBS can be organized in different ways but are typically scoped by time or duration and address both service system development and maintenance as well as service delivery as appropriate. Some of the services identified can be continuously delivered; others can be in response to ad-hoc requests. Both are specified in a (possibly future) service agreement.

Activities can be further organized along one or more dimensions. For example, in the case of product maintenance, activities could further be distinguished according to those activities that persist through the end of the life of the product (from product delivery through product disposal), activities related to managing and executing the service agreement, and activities related to an individual incident or service request.

Example Work Products

  1. Task descriptions
  2. Work package descriptions
  3. WBS


1. Develop a WBS based on the service strategy.

The WBS provides a scheme for organizing the work. The WBS should permit the identification of the following items:

  • Risks and their mitigation tasks
  • Tasks for deliverables and supporting activities
  • Tasks for skill and knowledge acquisition
  • Tasks for the development of needed support plans, such as configuration management, quality assurance, and verification plans
  • Tasks for the integration and management of nondevelopmental items

2. Define the work packages in sufficient detail so that estimates of tasks, responsibilities, and schedule can be specified.

The top-level WBS is intended to help gauge the work effort for tasks and organizational roles and responsibilities. The amount of detail in the WBS at this level helps in developing realistic schedules, thereby minimizing the need for management reserve.

3. Identify products and product components to be externally acquired.

Refer to the Supplier Agreement Management (SAM) (CMMI-SVC) process area for more information about managing the acquisition of products and services from suppliers.

4. Identify work products to be reused.