The Actors - End User and Car Rental Agency.
The story - End User Jack, has rented a self driving car from a car rental agency to get to the airport. He has to go through the hassle of driving his vehicle to the rental drop off point and then getting into the airport terminus.
Enter Valet Service. This app lets the user connect to a valet service. The valet service personall arrive at the airport, pick up the rental car and park it at the rental drop off point, there by saving time for the end user.