| Review Levels | Explanation | Comments | 
  
    | Formal-External | This artifact is part of the delivery at 
          a specific milestone and requires some form of approval by the customer, 
          the sponsor or some other external stakeholder. | The review record is configuration managed
      along with the artifact. For example, the Vision and the Business Case are artifacts that
    normally have to be reviewed by stakeholders.  | 
  
    | Formal-Internal | This artifact is formally reviewed internally
      by the project. | The review record is configuration managed
      along with the artifact. For example, the interfaces of design subsystems usually have to be
    reviewed and approved by several members of the project.  | 
  
    | Informal | This artifact is reviewed, but not formally
    approved. | The artifact is developed and maintained. It
    is normally not discarded after the project is complete and there isn't any review record. Design classes and components are
      typical examples of
    artifacts that are not formally reviewed. This can still mean that
    someone, perhaps a peer, will review it. | 
  
    | None | This artifact does not need to be reviewed or approved. | The artifact is created as work
    information. It is often a temporary artifact that is discarded after the
    project is complete. |