UMLR — UML 2.5: StateMachine Vertex needs to be made a kind of

In clause 14.3 dealing with state machine redefinition, State is declared as a kind of RedefinableElement (see Figure 14.37). This is necessary not only to allow States to be refined, but also because adding a Transition in an extending state machine necessarily has an impact on the "source" and "target" properties of the States that serve as the source and target (respectively) of that Transition. However, the source and target of a Transition is not necessarily a State; it could, in fact, be any kind of Vertex, such as a Pseudostate.

Consequently, it is necessary to declare Vertex as a kind of RedefinableElement. Since State is a kind of Vertex, the necessary change to the metamodel is to replace State (see figure 14.37) by Vertex