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Registrasion for Zookeepr Keeprs
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Things that are the same
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* You have an inventory of products
* Complete registrations are made up of multiple products
* Products are split into categories
* Products can be listed under ceilings
* Products can be included for free by purchasing other items
 * e.g. a Professional Ticket includes a dinner ticket
* Products can be enabled by user roles
 * e.g. Speakers Dinner tickets are visible to speakers
* Vouchers can be used to discount products

Things that are different
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* Ceilings can be used to apply discounts, so Early Bird ticket rates can be
  implemented by applying a ceiling-type discount, rather than duplicating the
  ticket type.
* Vouchers can be used to enable products
 * e.g. Sponsor tickets do not appear until you supply a sponsor's voucher
* Items may be enabled by having other specific items present
 * e.g. Extra accommodation nights do not appear until you purchase the main 
   week worth of accommodation.