Behaviour and State Change Models II

1. The sequence diagram below illustrates what happens when a passenger checks-in using an automatic check-in terminal in an airport. The terminal is connected to the Airline Information System (AIS). Write a scenario using natural language to describe the sequence of events from the user's point of view.

2. Redraw the statechart below, removing all the composite states and replacing all transitions to and from composite states with equivalent transitions between the remaining states.

3. The statechart below specifies a CD player. Suppose that the player is turned off when it is in the open state, with no CD in the drawer and the drawer open, and is then immediately powered on again.

• What state is the CD player after these operations?
• What is the physical condition of the drawer of the CD player?
• What will happen if the user presses the load button?
• What buttons would the user have to press in order to close the drawer of the CD player?

4. Draw using Together Control Center, a revised version of the statechart above modelling the requirement that the CD player when paused should remain paused even when "stop" and then "play" are pressed.