section Check In
  description   Message used during Check-In procedure.
  message Verify-Ticket The ticket is given for verification
  message Ticket-valid The ticket is valid
  message Ticket-invalid The ticket is not valid
  message Ticket-rejected The ticket is permanently rejected
  message Resolve-Ticket-issue An attempt is made to resolve the ticket problem
  message Load-Luggage The luggage is loaded to be inspected and weighted
  message Pay-for-Luggage The passenger payed for the excessive luggage.
  message Luggage-accepted The luggage is labeled and accepted
  message Luggage-too-heavy The luggage is too heavy
  message Luggage-odd-size The luggage has the wrong size
  message Seat-Preference Passenger expresses its seat preference
  message Issue-Boarding-Pass The boarding pass is issued
  protocol Airport The human airport protocol used in the interaction