ALTERNATE STRUCTURE CONCEPTS
The concept of a WBS as an outline is stressed in this book. An outline is both an organized description of the project work and a plan for the work to be accomplished. In developing the outline, you may identify work that was not initially contemplated, and you may eliminate work that is not part of the project. The final WBS may go through several stages as the project becomes defined. A normal WBS contains very brief descriptions of the work elements, like a sketchy topical outline. This kind of outline requires that the work be defined during the WBS development process, and the final products may include a SOW structured around the WBS or a WBS dictionary. In some cases, it may be preferable to just identify the work elements with phrases or sentences.
The kind of outline—WBS—you use should be determined by the project work structure itself, the culture of your organization, and your own thought processes. For most people, there is an interaction between defining work elements, thinking, and organizing. As you proceed in the development of a WBS, you will probably revise it more than once, rearranging the order and levels of work elements, adding work, and deleting work.
The preferred approach to the development of the WBS is to make it a team effort. In that manner, the team members become intimately involved in the project and the definition of the work to be performed. Having a team effort also helps ensure all the work is identified, because specialists and experts will make sure the WBS covers their specialty areas. When developing a WBS with a team, there are only two primary rules:
(1) The 100 percent rule.
(2) Project management should be a Level 2 WBS element.
All the other rules, such as those listed in Chapter 4, can be tailored to fit the culture and used as guidelines.
There are differing opinions as to the best structure for a WBS, and these alternative opinions are presented and discussed in this chapter. Translating the concept of the outline structure for writing into WBS, one could say that the best organizing principles are inherent in the project itself and in the way the project is to be implemented.
For example, a project that is to be implemented in several different cities may be best organized by structuring the work geographically at Level 2 and using one of the other types of structures at Level 3.
A project where one organization will complete all of its work and then pass it on to another organization for the next step may be best organized by process steps at Level 2. This is common in construction projects where the design is completed before the construction begins and in fact may be a requirement where design drawings are needed for the construction bidding process. Another project that involves the tightly integrated design, development, and fabrication of a prototype may be best organized by the structure of the deliverable product. Using the personal computer example, the principal alternate WBS constructs are shown in Figures 2-21 and 2-22.
Both of these WBSs should result in the same work packages and activities being defined, although the Product WBS is more in keeping with the focus being deliverables. The two WBSs present different perspectives of the work content. The choice will depend on the culture and structure of the organization, the managerial style of the project manager, and other factors. If the 100 percent rule is followed, the end result should be the same.
The WBS in Figure 2-22, although having a process flow, is not a “results-type” project. It is a project with a product focus that is structured with processes.
It is necessary to keep an open mind about how to structure a WBS and to allow the project itself to suggest its own organization, but still focusing on outputs.
Other kinds of breakdown structures to present project information are as follows:
Organizational Breakdown Structure (OBS) is a structure that is used to show which work components have been assigned to which organizational units. Preparing an OBS can be very confusing if the intent is to use it to define the work, because it is organization- or input-oriented. The focus in developing a WBS must be on the work, not on organizations of people.
One of the difficulties in developing a WBS is the necessity to move away from the paradigm of structuring work by organization function and instead to focus on the deliverable or output product. When structuring by organization, you are focusing on the inputs to the project, not the outputs. The OBS is useful to develop after the project activities are all defined in order to provide a report or schedule of all the activities that are the responsibility of a specific organization, such as “Engineering Design.” Most project management software systems make it easy to add an organization or responsibility code to identify the organization. In some software packages, these fields are identified as “OBS” fields. Rad categorizes the OBS as “the most readily available structure.” He cautions that because companies frequently go through large organizational changes, “care must be taken to use the most recent data and to make updates as changes continue to occur within the organization.”
Resource Breakdown Structure (RBS) is described as a variation of the OBS and is typically used when work components are assigned to individuals. Rad has a somewhat different perspective of the RBS than that presented in the PMBOK® Guide. He perceives the RBS as a logical and useful classification of the resources needed to accomplish a project’s objectives. He also recommends developing a resource pool that is essentially a catalog of all the resources available to a project. To accomplish cross-project resource planning, the coding or categorization scheme of the resources in the pool needs to be the same for each project. Figure 2-23 is an example developed by Rad.
FIGURE 2-23 Resource Breakdown Structure
A further discussion of resource pools is incorporated in the author’s book, Project Planning and Scheduling.
Bills of Material (BOM) present a hierarchical view of the physical assemblies, subassemblies, and components needed to fabricate a manufactured product, according to the PMBOK® Guide. However, a BOM, if available for a deliverable of a project, is useful for structuring the product section of the WBS. In fact, a summary or top-level BOM is essential for developing a WBS for most tangible products. A BOM by itself is not a WBS.
The PMBOK® Guide also makes reference to a Project Breakdown Structure (PBS) and indicates the PBS is fundamentally the same as a properly done WBS. The PBS was the term used in the 1960s, and occasionally since then, by some authors, and it eventually was dropped in favor of the WBS terminology. Archibald describes the PBS as identical to the WBS in his 1976 book.