5.3.1 Inputs to Scope Definition

.1 Scope statement. The scope statement is described in Section 5.2.3.1.

.2 Constraints. Constraints are described in Section 5.1.3.3. When a project is done under contract, the constraints defined by contractual provisions are often important considerations during scope definition.

.3 Assumptions. Assumptions are described in Section 4.1.1.5.

.4 Other planning outputs. The outputs of the processes in other knowledge areas should be reviewed for possible impact on project scope definition.

.5 Historical information. Historical information about previous projects should be considered during scope definition. Information about errors and omissions on previous projects should be especially useful.

5.3.2 Tools and Techniques for Scope Definition

.1 Work breakdown structure templates. A work breakdown structure (WBS, described in Section 5.3.3.1) from a previous project can often be used as a template for a new project. Although each project is unique, WBSs can often be “reused” since most projects will resemble another project to some extent. For example, most projects within a given organization will have the same or similar project life cycles and will thus have the same or similar deliverables required from each phase.
  Many application areas or performing organizations have standard or semi-standard WBSs that can be used as templates. For example, the U.S. Department of Defense has recommended standard WBSs for Defense Materiel Items. A portion of one of these templates is shown as Figure 5–2.

.2 Decomposition. Decomposition involves subdividing the major project deliverables or subdeliverables into smaller, more manageable components until the deliverables are defined in sufficient detail to support development of project activities (planning, executing, controlling, and closing). Decomposition involves the following major steps:

(1) Identify the major deliverables of the project, including project management. The major deliverables should always be defined in terms of how the project will actually be organized. For example:

   The phases of the project life cycle may be used as the first level of decomposition with the project deliverables repeated at the second level, as illustrated in Figure 5–3.

   The organizing principle within each branch of the WBS may vary, as illustrated in Figure 5–4.

(2) Decide if adequate cost and duration estimates can be developed at this level of detail for each deliverables. The meaning of adequate may change over the course of the project—decomposition of a deliverable that will be produced far in the future may not be possible. For each deliverable, proceed to Step 4 if there is adequate detail and to Step 3 if there is not—this means that different deliverables may have differing levels of decomposition.

(3) Identify constituent components of the deliverable. Constituent components should be described in terms of tangible, verifiable results to facilitate performance measurement. As with the major components, the constituent components should be defined in terms of how the work of the project will actually be organized and the work of the project accomplished. Tangible, verifiable results can include services as well as products (e.g., status reporting could be described as weekly status reports; for a manufactured item, constituent components might include several individual components plus final assembly). Repeat Step 2 on each constituent component.

(4) Verify the correctness of the decomposition:

   Are the lower-level items both necessary and sufficient for completion of the item decomposed? If not, the constituent components must be modified (added to, deleted from, or redefined).

   Is each item clearly and completely defined? If not, the descriptions must be revised or expanded.

   Can each item be appropriately scheduled? Budgeted? Assigned to a specific organizational unit (e.g., department, team, or person) who will accept responsibility for satisfactory completion of the item? If not, revisions are needed to provide adequate management control.

5.3.3 Outputs from Scope Definition

.1 Work breakdown structure. A work breakdown structure is a deliverable-oriented grouping of project elements that organizes and defines the total scope of the project: work not in the WBS is outside the scope of the project. As with the scope statement, the WBS is often used to develop or confirm a common understanding of project scope. Each descending level represents an increasingly detailed description of the project elements. Section 5.3.2.2 describes the most common approach for developing a WBS. A WBS is normally presented in chart form as illustrated in Figure 5–2, 5–3, and 5–4; however, the WBS should not be confused with the method of presentation—drawing an unstructured activity list in chart form does not make it a WBS.
  Each item in the WBS is generally assigned a unique identifier; these identifiers can provide a structure for a hierarchical summation of costs and resources. The items at the lowest level of the WBS may be referred to as work packages, especially in organizations that follow earned value management pratices. These work packages may in turn be further decomposed as described in a subproject work breakdown structure. Generally,this type of approach is used when the project manager is assigning a scope of work to another organization, and this other organization must plan and manage the scope of work at a more detailed level than the project manager in the main project. These work packages may be further decomposed in the project plan and schedule, as described in Sections 5.3.2.2, 6.1.2.1.
  Work component descriptions are often collected in a WBS dictionary. A WBS dictionary will typically include work package descriptions as well as other planning information such as schedule dates, cost budgets, and staff assignments.
  The WBS should not be confused with other kinds of “breakdown” structures used to present project information. Other structures commonly used in some application areas include:

   Contractual WBS (CWBS), which is used to define the level of reporting that the seller will provide the buyer. The CWBS generally includes less detail than the WBS used by the seller to manage the seller’s work.

   Organizational breakdown structure (OBS), which is used to show which work components have been assigned to which organizational units.

   Resource breakdown structure (RBS), which is a variation of the OBS and is typically used when work components are assigned to individuals.

   Bill of materials (BOM), which presents a hierarchical view of the physical assemblies, subassemblies, and components needed to fabricate a manufactured product.

   Project breakdown structure (PBS), which is fundamentally the same as a properly done WBS. The term PBS is widely used in application areas where the term WBS is incorrectly used to refer to a BOM.

.2 Scope statement updates. Include any modification of the contents of the scope statement (described in 5.2.3.1). Appropriate stakeholders must be notified as needed.