Level 2 are further subdivided at Level 3. The two largest elements at Level 3 each represent only 17% of the total scope of the project. These larger elements could be further subdivided using the progressive elaboration technique described above. This is an example of the product-based approach (which might be end-product or deliverable or work-based), as compared to phased approach (which might be gated stages in a formal Systems development life cycle, or forced events (e.g. quarterly updates or a fiscal year rebudgeting), or a skills/roles based approach. WBS design can be supported by software (e.g. a spreadsheet) to allow automatic rolling up of point values. Estimates of effort or cost can be developed through discussions among project team members. This collaborative technique builds greater insight into scope definitions, underlying assumptions, and consensus regarding the level of granularity required to manage the projects. See also Common Arrangement of Work Sections List of project management topics Project anatomy Project management software Project planning Structure chart MECE principle Timeblocking References Further reading (Note: The Second Edition is an extensive re-write of the Practice Standard.) (Note: This new book is essentially a facilitator's guide for planning a project based on the WBS.) External links how to create work breakdown structure WBS using standard Division of work EverySpec.Com copies of MIL-HDBK-881 versions ASSIST entry for MIL-HDBK-881C Defense Acquisition University ACQ101 Summary for Work Breakdown Structures How to Make a Work Breakdown Structure NASA Work Breakdown Structure Handbook, NASA/SP-2010-3404, January 2010 Business process modelling Schedule (project management) Systems engineering