Let us consider airport check-in and security screening. The airport offers "group check-in" and "individual check-in". "Group check-in" is only for groups of tourists. The tour guide is responsible for checking in his/her group members. Other passengers including able-bodied passenger, minor (child), and passenger with special needs (e. g. with disabilities) use "individual check-in". All the passengers should pass the security screening. In addition, passengers may or may not have luggage. If they have no luggage, they do not have to do baggage check-in.