Customizing the metamodel : Diagrams: Creating and modifying : Creating roadmap-style diagrams : Diagram : When is the diagram synchronized?
  
When is the diagram synchronized?
The diagram is synchronized with underlying definitions when it is opened, on pressing F3, and on OKing any change to a Project or Milestone definition.
The diagram is supposed to refresh following modification of Project or Milestone definitions so that it will show the proper representation.