Project management groups

  "in the complex project landscape effective integration requires management approaches that allow for a flexible creative and adaptive approach by the project team in response to the changing characteristics of the project, organization, and cultural environment and the dynamics of the organization".  This week you learned about process groups used in the project management lifecycle.  In your experience, are all these deliverables necessary?  Provide two deliverables that all projects, regardless of methodology, should leverage and two deliverables that may not be necessary and why?