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{tabsetup:1. Purpose|2. Definition|3. The Basic WBS|4. Common Issues|5. Resources}

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h1. 1. Purpose

Topic 7.17 provides guidance on the development of a work breakdown structure (WBS) for software on projects.  The WBS provides a common planning framework to use in estimating the scope of a project.

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h1. 2. Definition

Per the [NASA Systems Engineering Handbook|https://nen.nasa.gov/syseng/NASA-Systems-Engineering-Handbook.pdf] (Section 6.1.2.1) ^1^, a work breakdown structure is a hierarchical breakdown of the work necessary to complete a project.  The WBS can be product or process oriented.  A product-oriented WBS has work activities grouped by the product or service they support.  A process-oriented WBS has work activities associated with the processes used included in the appropriate WBS element. ^3^  The WBS provides the framework to plan, organize, and control a project. ^2^ 

Excellent information on the development and usage of the WBS can be found in NASA/SP-2010-3404 [NASA Work Breakdown Structure (WBS) Handbook.|http://ntrs.nasa.gov/search.jsp?R=20110012671&hterms=wbs+handbook+wbs&qs=Ntx%3Dmode%2Bmatchallany%7Cmode%2520matchall%26Ntk%3DAll%7CAll%26N%3D0%26Ntt%3Dwbs%7Cwbs%2520handbook#.T3CNkS3IkBQ.email] ^4^   Additionally, both the NASA Systems Engineering Handbook ^1^ and the "CMMI for Development, Guidelines for Process Integration and Product Improvement" ^2^ provide further guidance on the development of WBS structures containing software.  The NASA Software Engineering curriculum, especially {term:SWE 301} ^3^ , addresses the use of the WBS for software on projects. These resources are cited in tab five of this guidance topic. 


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h1. 3. The Basic WBS

A project's software may be a stand-alone system or exist as part of a larger system or project.  For example, for a space flight project, software may be shown under the Avionics subsystem.  For both types, the WBS developer needs to be aware of the responsibilities required of his or her project. 


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The WBS should be updated iteratively over the project life cycle .  The initial WBS is used for early estimating of cost and schedule.  The detailed WBS helps organize and control the work done by populating the project's cost plans and schedule.  
A companion WBS dictionary should also be developed that fully describes the work being done including the title and objective of the element, expected products/services from each element, and the dependencies between elements.


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h1. 4. Common Issues

There are several work activities that are often forgotten  in developing the WBS:

* Process planning and monitoring activities
* Requirement engineering activities
* Formal review activities
* Development activities
* Stakeholder activities
* Training activities
* Planning, documenting, and tracking of commitments from other organizations

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h1. 5. Resources

The following are excellent resources for help with developing and using a WBS.
# [NASA Systems Engineering Handbook|https://nen.nasa.gov/syseng/NASA-Systems-Engineering-Handbook.pdf], NASA SP-2007-6105, Rev1, NASA Headquarters, 2007.  
# Chrissis, M.B., et al. (March, 2011). CMMI for Development Guidelines for Process Integration and Product Improvement; Third Edition. SEI Series in Software Engineering. Addison-Wesley Professional.
# APPEL Software Engineering Management 301 (SWE 301). Course from APPEL: Academy of Program/Project & Engineering Leadership. Located via the NASA website at http://www.nasa.gov/offices/oce/appel/curriculum/courses/appel_swe-301.html.
# NASA SP-2010-3404. ["NASA Work Breakdown Structure (WBS) Handbook."|http://ntrs.nasa.gov/search.jsp?R=20110012671&hterms=wbs+handbook+wbs&qs=Ntx%3Dmode%2Bmatchallany%7Cmode%2520matchall%26Ntk%3DAll%7CAll%26N%3D0%26Ntt%3Dwbs%7Cwbs%2520handbook#.T3CNkS3IkBQ.email]  NASA Headquarters. January 2010.


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