Editing Work breakdown structure (section)

=== Level of detail ===
One must decide when to stop dividing work into smaller elements. For most projects, a hierarchy of two to four levels will suffice. This will assist in determining the duration of activities necessary to produce a deliverable defined by the WBS. There are several heuristics or "rules of thumb" used when determining the appropriate duration of an activity or group of activities necessary to produce a specific deliverable defined by the WBS.

* The first is the "80-hour rule" which means that no single activity or group of activities at the [[#Terminal element|lowest level of detail of the WBS]] to produce a single deliverable should be more than 80 hours of effort.
* The second rule of thumb is that no activity or group of activities at the [[#Terminal element|lowest level of detail of the WBS]] should be longer than a single reporting period. Thus if the project team is reporting progress monthly, then no single activity or series of activities should be longer than one month long.
* The last heuristic is the "if it makes sense" rule. Applying this rule of thumb, one can apply "common sense" when creating the duration of a single activity or group of activities necessary to produce a deliverable defined by the WBS.

==== Work package ====
According to the [[Project Management Institute]], a '''work package''' is the "lowest level of the work breakdown structure for which cost and duration are estimated and managed."{{sfn|Project Management Institute|2021|loc=§Glossary Section 3. Definitions}}

A work package at the activity level is a task that:

* can be realistically and confidently estimated;
* makes no sense practically to break down any further;
* can be completed in accordance with one of the heuristics defined above;
* produces a deliverable which is measurable; and
* forms a unique package of work that can be outsourced or contracted out.

==== WBS dictionary ====
If the WBS element names are ambiguous, a WBS dictionary can help clarify the distinctions between WBS elements. The WBS Dictionary describes each component of the WBS with [[Milestone (project management)|milestones]], deliverables, activities, scope, and sometimes dates, [[Resource (project management)|resources]], costs, quality.
According to the [[Project Management Institute]], the WBS dictionary is defined as a "document that provides detailed deliverable, activity, and scheduling information about each component in the work breakdown structure."
{{sfn|Project Management Institute|2021|loc=§Glossary Section 3. Definitions}}

====Coding scheme====
It is common for work breakdown structure elements to be numbered sequentially to reveal the hierarchical structure. The purpose of the numbering is to provide a consistent approach to identifying and managing the WBS across like systems regardless of vendor or service.<ref>MIL-STD-881C, Work Breakdown Structures for Defense Materiel Items, 3 October 2011, ¶4.3</ref> For example, 1.1.2 Propulsion (in the example below) identifies this item as a Level 3 WBS element, since there are three numbers separated by two [[Decimal separator|decimal points]]. A coding scheme also helps WBS elements to be recognized in any written context, such as progress tracking, scheduling, or billing, and allows for mapping to the WBS Dictionary.{{citation needed|date=April 2024}}  It is a preferred practice that the [[Statement of work]] or other contract descriptive include the same section terms and hierarchical structure as the WBS.

A practical example of the WBS coding scheme is<ref>MIL-STD-881C, Work Breakdown Structures for Defense Materiel Items, 3 October 2011 Appendix A, ¶A.3</ref>

''1.0 Aircraft System''
:''1.1 Air Vehicle''
::''1.1.1 Airframe''
:::''1.1.1.1 Airframe Integration, Assembly, Test, and Checkout''
:::''1.1.1.2 Fuselage''
:::''1.1.1.3 Wing''
:::''1.1.1.4 Empennage''
:::''1.1.1.5 Nacelle''
:::''1.1.1.6 Other Airframe Components 1..n (Specify)''
::''1.1.2 Propulsion''
::''1.1.3 Vehicle Subsystems''
::''1.1.4 Avionics''
:''1.2 System Engineering''
:''1.3 Program Management''
:''1.4 System Test and Evaluation''
:''1.5 Training''
:''1.6 Data''
:''1.7 Peculiar Support Equipment''
:''1.8 Common Support Equipment''
:''1.9 Operational/Site Activation''
:''1.10 Industrial Facilities''
:''1.11 Initial Spares and Repair Parts''