What is the main distinction between external and internal transitions?

The main distinction between external and internal transitions lies in the types of behaviors they execute. External transitions are characterized by three sequential behaviors: exit behavior, effect behavior, and entry behavior. When an external transition occurs, the system first exits the current state, then executes any effect behaviors associated with that transition, and finally enters the new state by executing entry behaviors. This sequence effectively alters the system's state and its context, making the transition noticeable within the system's operation.

Internal transitions, on the other hand, only execute the effect behavior. They do not involve exiting the current state or entering a new one, which means that the system remains in the same state throughout the process. This type of transition allows for changes in conditions or effects while the system is still considered to be in a stable state, thus keeping the state contextually consistent.

Understanding this distinction is crucial for system modeling, as it determines how a system responds to certain events while maintaining or changing its state. Hence, recognizing that external transitions involve a complete state change with multiple behaviors executed, while internal transitions focus solely on effects without altering the state, is essential for accurately modeling system dynamics.