A work breakdown structure (WBS) in project management and systems engineering, is a tool used to define and group a project's discrete work packages in a way that helps organize and define the total work scope of the project. A work breakdown structure element may be a product, data, a service, or any combination. A WBS also provides the necessary framework for detailed cost estimating and control along with providing guidance for schedule development and control. Additionally the WBS is a dynamic tool and can be revised and updated as needed by the project manager.