Editing Work breakdown structure (section)

===  100% rule ===
An important design principle for work breakdown structures is called the 100% rule.<ref>''Effective Work Breakdown Structures'' By Gregory T. Haugan, Published by Management Concepts, 2001, {{ISBN|1567261353}}, p.17</ref> It has been defined 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 100% rule is one of the most important principles guiding the development, decomposition, and evaluation of the WBS. 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.<ref>''Practice Standard for Work Breakdown Structures (Second Edition)'', published by the [[Project Management Institute]], {{ISBN|1933890134}}, page 8</ref>

==== Mutually exclusive elements ====
[[Mutually exclusive]]: In addition to the 100% rule, there must be no overlap in scope definition between different elements of a work breakdown structure. This ambiguity could result in duplicated work or miscommunications about responsibility and authority. Such overlap could also confuse project cost accounting.