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Work Breakdown Structure (WBS) is a tool for simplifying the complexity of a particular task of a project. The task is broken down into smaller components that cannot be divided further. This deliverable-oriented structure makes an activity manageable and achievable to a greater extent.
In the PMBOK, WBS is defined as “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."
This project management tool organizes the activities and lays down an outline or map for a project. Extensive brainstorming has to be done to identify the various levels of efficient WBS.
Purpose of Work Breakdown Structure
The purpose of using a Work Breakdown Structure for an activity is to:
- Give a unique identity to each activity
- Recognize the distinct nature of the broad activity
- Estimate the time and cost required for an activity
- Monitor and control the task
- Portray the entire scope of the activity, all the deliverables, and milestones
Although a WBS has a hierarchical decomposition of work, it does not necessarily specify the order of work to be done. The schedule has to be made separately; however, an interface between the two could be devised.
Types of Work breakdown Structures
Work Breakdown Structure has two main types :
1. Phase-oriented WBS
2. Deliverable-oriented WBS
- Phase-Oriented Work Breakdown Structure
The phase-oriented Work Breakdown Structure is also referred to as Verb-oriented, Activity or Task-oriented, or Process-oriented WBS. The project deliverables are defined in terms of actions to be taken to attain the final product. Example: test, design, transfer, etc.
2. Deliverable-oriented Work breakdown Structure
The deliverable-oriented Work Breakdown Structure is also known as Noun-oriented, Entity-oriented or Product-oriented WBS. In this type of WBS, the functions or physical components that make up the deliverable define the project work Example: Foundation, Design Engine, Module 1, etc.
Cost breakdown, time-phased, profit-center, etc. are some other types of WBS.
Guidelines for making an Effective Work Breakdown Structure
1. The 100% Rule
The 100% Rule is the most important principle for designing a WBS. This rule states that the WBS should include all the work identified by the project scope and must have all the deliverables that have to be completed - internal, external, and interim.
2. Level Approach
There are two approaches with which the Work Breakdown Structure can be developed.
- Top-Down Approach: In this approach, the project is divided into sub-projects. This is done until the task can be defined and estimated. This approach is more popular and is known for giving an accurate WBS.
- Bottom-Up Approach: In this approach, the lowest level activities are to be put down first. This could be a tedious process and requires a lot of brainstorming.
3. Mutually Exclusive Activities
An activity shouldn’t be repeated twice in a WBS. This could lead to confusion during execution and would also require additional resources.
4. Level of Detail
One must know when to stop breaking down an activity. Stop breaking down the task when the estimate of the desired level of accuracy can be attained.
5. Absence of Symmetry
Not all activities have the same number of sub-activities. Thus, a Work Breakdown Structure doesn’t have to be symmetric or have the same bottom level.
6. Additional features
As mentioned earlier, the WBS does not depict the order of activities. To do so, a code can be given to all the tasks. Different coding arrangements are available but use the one which suits the organization or product structure for reporting and control.
Modifications can be made in a WBS to show more details.
In the above image, work allocation to the contractors has been delineated.
Criteria for WBS
An effective work breakdown structure must meet the following criteria:
- Justified Logic: The structure of the WBS should be rational and easy to understand.
- Hierarchy Approach: Data should be specified clearly following the hierarchy of tasks. It should be specified in such a way that the summary of all the activities can be easily done.
- Collaborative Structure: While making an interface, the WBS structure should have enough precision for data generation.
WBS is used for simplifying the complexity of a particular task in a project.
Phase-oriented WBS, Deliverables- Oriented WBS, Cost breakdown, time-phased WBS, profit-center WBS are the different types of WBS.
The WBS makes the deliverables more concrete and precise so that all stakeholders are able to understand what has to be accomplished.