Now that the project scope is in place and identifies the work that has to be done, this total quantum of work will have to be decomposed. Decomposition, in project management terms, is nothing but breaking down into the least possible 'workable' parts. Breaking down of the total work will begin with the Product Breakdown Structure. In other words, the product is broken down theoretically into smaller components, divisions, or departments. It is from the breaking down of the product that we arrive at the work related to each decomposed product section.
The Work Breakdown Structure, once understood, will highlight work along different levels beginning with the scope of the project (project name) until it has reached the level where it cannot be broken down any further. The lowest level of work that can be done is called a 'work package'. There can be many work packages, where a group of work packages may be linked to a single parent task, a level above it.
By taking a look at a Work Breakdown Structure, one can see the WBS-Scope Relationship. The WBS simply supports the scope by detailing the total quantum of work outlined in the scope. Without the scope statement, it would be difficult to create the Work Breakdown Structure, and without the WBS, it would be difficult for the scope to be understood.
Any work not mentioned in the WBS is outside the scope of the project and is not to be carried out.