Executable UML models are nowadays gaining interest in embedded systems design. This domain is strongly devoted to the modeling of reactive behavior using StateChart variants. In this context, the direct execution of UML State Machines is an interesting alternative to native code generation approaches since it significantly increases portability. However, fully featured UML 2.0 State Machines may contain a broad set of features with complex execution semantics that differ significantly from other StateChart variants. This makes their direct execution complex and inefficient. In this paper, we demonstrate how such State Machines can be represented using a small subset of the UML State Machine features that enables efficient execution. We describe the necessary model transformations in terms of graph transformations and discuss the underlying semantics and implications for execution.