What is a Work Breakdown Structure?
Breaking work into trivial tasks is a common productivity practice used to make the work more manageable and amicable. For projects, the Work Breakdown Structure (WBS) is the tool that utilizes this technique and is one of the most significant project management documents. It unaided integrates scope, cost and schedule baselines ensuring that project plans are in orientation.
The Project Management Institute states the Work Breakdown Structure as a “deliverable oriented hierarchical decomposition of the work to be executed by the project team.” There are two types of WBS: 1) Deliverable-Based and 2) Phase-Based. The most common and preferred approach is the Deliverable-Based approach. The main differences between the two approaches are the Fundamentals identified in the first Level of the WBS.
A good WBS is simply one that makes the project more manageable. Every project is different; every project manager is different and every WBS is diverse. So, the right WBS is the one that best answers the question, “What structure makes the project more adaptable?”
Applying the Work Breakdown Structure to the project management lifecycle
The Prominence of the Work Breakdown Structure
Knowledgeable project managers know that many things can go erroneous in projects, regardless of how successfully the work is planned and executed. Component or full-project failures, when they do transpire, can often be traced to a poorly developed or unreal WBS. A poorly constructed WBS can result in adverse project outcomes including ongoing, repeated project re-plans and extensions, vague work assignments, scope creep or unmanageable, frequently changing scope, budget overrun, missed deadlines and incompetent new products or delivered features.
The WBS is an introductory building block to initiating, planning, executing, and monitoring and controlling processes that are used to manage. There are many project management tools and techniques that use the WBS or its components as input. For example, the WBS utilizes the project charter as its preliminary point. The high-level elements in the WBS should match, word-for-word, the nouns used to describe the consequences of the project in the scope declaration. In addition, the resource breakdown structure (RBS) describes the project’s resource organization and can be used in aggregation with the WBS to define work package assignments. The WBS Glossary outlines, details, and clarifies the various fundamentals of the WBS. The network diagram is a sequential arrangement of the work defined by the WBS and the elements of the WBS are starting points for defining the activities included in the project agenda.
The WBS is used as a starting point for scope management and is essential to other PMI processes, and, as a result, the standards that define these processes explicitly or implicitly rely on the WBS. Standards that take advantage of the WBS either use the WBS as an input or integrate the WBS as the preferred tool to develop the scope definition.
A WBS, as defined in the PMBOK® Guide—Third Edition is “a deliverable-oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables. It organizes and defines the total scope of the project. Each descending level represents an increasingly detailed definition of the project work. The WBS is decomposed into work packages. The deliverable orientation of the hierarchy includes both internal and external deliverables.”
With this definition, it is clear the WBS provides an unambiguous statement of the objectives and deliverables of the work to be performed. It represents an explicit description of the project’s scope, deliverables and outcomes—the “what” of the project. The WBS is not a description of the processes followed to perform the project…nor does it address the schedule that defines how or when the deliverables will be produced, but rather is specifically limited to describing and detailing the project’s outcomes or scope. The WBS is a foundational project management component, and as such, is a critical input to other project management processes and deliverables such as activity definitions, project schedule network diagrams, project and program schedules, performance reports, risk analysis and response, control tools, or project organization.
Defining the WBS
The upper levels of the WBS typically echo the major deliverable work areas of the project, disintegrated into logical groupings of work. The content of the upper levels may vary, depending on the type of project and industry involved. The lower WBS elements provide appropriate detail and focus for support of project management processes such as schedule development, cost estimating, resource apportionment, and risk assessment. The lowest-level WBS components are called work packages and contain the definitions of work to be performed and tracked. These can be later used as input to the scheduling process to support the elaboration of tasks, activities, resources, and milestones which can be cost estimated, monitored, and meticulous.
Few of the key characteristics of high-quality work breakdown structures (are outlined below:
• A central attribute of the WBS is that it is “deliverable orientated” where deliverable is defined as: “Any unique and demonstrable product, result, or competence to perform a service that must be produced to complete a process, phase or project.” In this context, “oriented” means allied or positioned with respect to deliverables
• A superfluous key attribute of the WBS is that it is a “hierarchical decomposition of the work.” Decomposition is “a preparation technique that segments the project scope and project deliverables into smaller, more manageable components, until the project work associated with accomplishing the project scope and deliverables is defined in adequate detail to support executing, superseding, and controlling the work”
• The 100% Rule is one of the most important principles guiding the development, decomposition, and evaluation of the WBS. This rule states that the WBS includes 100% of the work defined by the project scope and, by doing so, captures all of the deliverables—internal, external, and interim—in terms of work to be completed, including project administration.
• The WBS can be represented in a variety of ways, including graphical, textual, or tabular views. The form of depiction should be chosen based on the needs of the particular project.
Why use a WBS in project management?
There are a number of reasons why breaking down a large project is advantageous. It helps you to:
• Estimate the cost of a project.
• Establish dependencies.
• Standardize a project timeline and develop a schedule.
• Transcribe a statement of work (or SOW, one of your other acronyms).
• Assign responsibilities and clarify roles.
• Track the progress of a project.
• Identify risk.
All of these benefits essentially ascend from working with chunks of a project that you can accurately visualize rather than trying to résumé and interpret a mysterious and prodigious task in one fell swoop.
How to create a work breakdown structure:
1. Record the overarching objective you are trying to accomplish. This objective could be anything from developing a new software feature to building a missile.
2. Divide the overarching project into smaller and smaller pieces, but stop before you get to the point of listing out every action that must be taken. Remember to focus on concrete deliverable rather than actions.
3. Depending on the nature of your project, start dividing by project phases, specific large deliverables, or sub-tasks.
Tips for making a work breakdown structure
As you make a work breakdown structure, use the following rules for best results:
• The 100% rule. The work represented by your WBS must include 100% of the work necessary to complete the all-encompassing goal without including any superfluous or unrelated work. Also, child tasks on any level must account for all of the work essential to complete the parent task.
• Mutually exclusive. Do not embrace a sub-task twice or account for any amount of work twice. Doing so would violate the 100% rule and will result in inaccuracies as you try to determine the resources necessary to complete a project.
• Outcomes, not actions. Remember to focus on deliverables and outcomes rather than actions. For example, if you were building a bike, a deliverable might be “the braking system” while actions would include “calibrate the brake pads.”
• The 8/80 rule. There are numerous ways to decide when a work package is small enough without being too trivial. This rule is one of the most common suggestions—a work package should take no less than eight hours of effort, but no more than 80. Other rules advocate no more than ten days (which is the same as 80 hours if you work full time) or no more than a typical reporting period. In other words, if you report on your work every month, a work package should take no more than a month to complete. When in doubt, apply the “if it makes sense” rule and use your best verdict.
• 3 levels. Generally speaking, a WBS should comprise about three levels of detail. Some branches of the WBS will be more subdivided than others, but if most branches have about three levels, the scope of your project and the level of aspect in your WBS are about right.
• Make assignments. Every work package should be dispensed to a specific team or individual. If you have made your WBS well, there will be no work overlay so responsibilities will be strong and clear.