Which of the following is a true statement regarding state transition diagrams?

State transition diagrams are primarily used to model the behavior of a system by depicting its states and the transitions between those states. These diagrams focus on illustrating the valid transitions that are possible within the system's defined state space.

The correct answer highlights that state transition diagrams are designed to show only the valid transitions between states, which are the scenarios that can occur during the operation of a system. The emphasis is on how a system can move from one legitimate state to another based on certain inputs or conditions. This clear representation helps in understanding the dynamic behavior of the system without the clutter of invalid transitions, which could introduce confusion regarding the system's expected functionality.

Valid transitions are essential in ensuring that the diagram accurately reflects the operational flow and behavior when different inputs are provided. This allows stakeholders to analyze, verify, and validate the logic of the system being modeled effectively.

In summary, state transition diagrams are focused on valid transitions to help visualize and understand the permissible interactions within the system rather than detailing every possible scenario, especially those that are not valid.