An activity also has a creator, a name, a description, and a flag indicating if it is available. We define the organizers' roles and their responsibilities. In addition, we store of which activity this event is an instance. This is for hooking up to ecommerce. An organizer role is an official position for that event.
Organizers are people who fill an organizer role position.
Registrations For each person who registers for an event, we record a bunch of information. This helps the organizations understand who is coming to their events and why. It also helps the organization accomodate its attendees' needs and group them together. There is one registration for each person who wants to attend. Registrations can have different states.