The web service function and goals for registration sign$-$in to be used by conference greeters is that it allows users to enter a person's name to see if they have already registered, sends data to a server as to the time that each attendee arrived at the conference, confirms whether registered attendees already purchased a ticket, allows non registered attendees to pay the ticket price and registered. Why would conference greeters use the registered sign in before, during, or after the conference?