What are the special features of edges?
UML includes edge types whose source elements allow for only one outgoing edge and whose target elements allow for only one incoming edge.
For example, a class may have only one outgoing edge of the owningPackage type to a package. This is controlled and managed by the system.
Example 12.
A class in a diagram has an edge of the owningPackage type to the package P1. If an edge of the same type is then drawn from the class to a package P2, the edge to package P1 is deleted. Furthermore, on the Explorer tab, the class is moved into the package P2.
If the class was nested in the package P1 in a diagram, the nesting is removed, but the presentation of the class remains in the diagram.