Customizing the metamodel : Diagrams: Creating and modifying : Creating roadmap-style diagrams : Diagram : Can a dependency line be drawn between two Milestones?
  
Can a dependency line be drawn between two Milestones?
A Dependency line may be drawn between two Milestones – this would usually be done between different Projects.
This shows the flow of information between two milestones or points in a project, so the acceptable situation is where information flows from a point early in the project to a point later in the project.