Work Breakdown Structure (WBS) was initially developed by the U.S. defense establishment, and it is described in Military Standard (MIL-STD) 881B (25 Mar 93) as follows: “A work breakdown structure is a product-oriented family tree composed of hardware, software, services, data and facilities …. [it] displays and defines the product(s) to be developed and/or produced and relates the elements of work to be accomplished to each other and to the end product(s).”
A project can be made more manageable by breaking it down into individual components that together are known as WBS. Thus, it is a result-oriented family structure that captures all the work of a project in an organized way. It answers “what” of the project rather than the “who”, “how” or “when” part of the project. That is, it is a clear description of the project deliverables and scope, and not a description of the process or the schedule of the project.
It facilitates other project management processes such as estimation, scheduling, resource allocation and even risk analysis of the project.
Is WBS process-oriented or product-oriented?
Though the initial definition of WBS was to create a product-oriented family structure, subsequently it was made flexible to support process-oriented family structure. WBS can be built using verbs or nouns. If the results of the project are more of verbs then a verb-based (or process-based) WBS is recommended.
WBS Design Principles
100% Rule: Practice Standard for Work Breakdown Structures (Second Edition), published by the Project Management Institute (PMI) defines the 100% Rule as follows:
The 100% Rule…states that the WBS includes 100% of the work defined by the project scope and captures ALL deliverables – internal, external, interim – in terms of the work to be completed, including project management. … The rule applies at all levels within the hierarchy: the sum of the work at the “child” level must equal 100% of the work represented by the “parent” and the WBS should not include any work that falls outside the actual scope of the project, that is, it cannot include more than 100% of the work… It is important to remember that the 100% rule also applies to the activity level. The work represented by the activities in each work package must add up to 100% of the work necessary to complete the work package.
Focus on planned outcomes and not planned actions
Best approach to adhere to 100% rule is to define the WBS elements in terms of outcomes or results, rather than in actions. In product development, the hierarchy is made up of components that make up an item and hence called product breakdown structure. When the work is divided by phases, it must be ensured each phase is clearly separated by deliverables with entry and exit criteria defined.
Mutually exclusive elements
In addition to 100% rule, it is important there is no overlap between in “what” needs to be achieved by two elements in WBS. If there is an ambiguity, it may result in duplicated work or miscommunication. This can be avoided, by mantaining a WBS dictionary. The dictionary describes each WBS element with scope, deliverables, activities, resources and even dates.
WBS Coding Scheme
WBS elements are numbered sequentially to reveal the hierarchy structure. For example blogger.sai.june.wbs, indicates this post is for the month of June submitted by sai in blogger. WBS codes can be letters and numbers (or even combination) that helps to identify the relationship among the tasks and organizes the project.