Different programs have different levels of complexity. Complex programs require a WBS to manage the deliverables and schedule, while simpler programs may not require a WBS. During the creation of the plan, you can specify whether the plan is supposed to be managed through a WBS. If you do this, the Manage WBS property is set on the plan, program, project, and sub projects, allowing the creation of the WBS root element (the top element of the WBS structure) as well as the plan object. The system associates the WBS root element with the plan object and the two objects have the same name.You can set properties on the plan and WBS root such that they behave differently.