Work Breakdown Structure (WBS)

Work Breakdown Structure (WBS) is a tool used in project management context that divide in different levels of details a deliverable-oriented project in hierarchical order. The main objective is to support the project manager by giving an overview of different steps, resources and costs involved in the project. Moreover during the project executions may include the percentage of steps completed this ensure better control and guidance in case during the project development may occur any changes. It is graphically represented by a hierarchical tree, where the job of each element is given by the sum of elements underneath connected (sublevels). These elements may represent a product, data, service or any combination thereof.

History

The WBS was initially developed by the U.S. defense, back to the 1950’s and 60’s, in cooperation with NASA they were adopting the Program Evaluation and Review Technique (PERT) . During 1962, United State Airforce released “STUDY OF METHODS FOR EVALUATION OF THE PERT/COST MANAGEMENT SYSTEM” in this document was mention WBS as a useful tool for Controlling and planning large acquisition projects . As understandable, most of NASA projects involves many actors (contractors) with totally different task. However, all of them are parts of the same project and works for the same final scope. The WBS was used to ‘‘ . . . ensure that the total project is fully planned and that all derivative plans contribute directly to the desired objectives’’ (NASA, 1962). After, this first approach NASA decide to keep update this document because believed valid and useful. In 1968, due to its success, the Department of defense released "Work Breakdown Structures for Defense Materiel Items" (MIL-STD-881), a military standard procedure which is obligatory for all programs under the Department of defense. This standard is constantly updated, the latest version refers tp 2001 . Project Management Institute (PMI) during 1987 started to enlarge these collections of documents for non-military purpose as result The Project Management Body of Knowledge (PMBOK) has been release. The first version is from 1987, and other versions have been released during (987, 1996, 2000, 2004, 2009, 2013 4. The main concept of subdividing different activities through different levels remain the same of the early years. However, the approach goes from “A task- oriented ‘family tree’ of activities 1987” PMBOKfirst Guide to “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” (PMBOK Guide — Third).

On one hand, the documents from PMI gives an overview of the WBS concept, on the other hand, the document released from the Department of Defense can be considered as a Handbook.