An <UnTicketed> element is included in a <Tickets> element if there is no ticketing in operation for an <Event>.
An <UnTicketed> event is for ``first come first served'' events. It should not be utilised if the <Event> has free admission, but a limited number of places which can be pre-booked in advance. In this case the <Tickets> should contain a <TicketType> with a <Price> of 0.00. You cannot utilise an <UnTicketed> element as well as a <TicketType>.
An <UnTicketed> event may still have limited capacity and may reach the point where nobody else is permitted access, but it is not possible to reserve your place in advance.