// element definitions
site((Category |Item | Person | OpenAuction | ClosedAuction)*)
OpenAuction(id, open, sell, bid*)
 open(itemref)
 sell(personref)
 bid(personref, stamp)
   stamp(date, time, increase)
ClosedAuction(id, closed, buy, sell)
 closed(itemref)
 buy(personref)
 sell(personref)
Item(id, inclusion)
 inclusion(categoryref)
Category(id, relate*)
  relate(categoryref)
Person(id, interest*, watch*)
  interest(categoryref)
  watch(openauctionref)

// key constraints
KEY(OpenAuction.id)
KEY(ClosedAuction.id)
KEY(OpenAuction.open.itemref)
KEY(ClosedAuction.closed.itemref)
KEY(Item.id)
KEY(Category.id)
KEY(Person.id)

// foreign key constraints
KEYREF(open.itemref --> Item.id)
KEYREF(closed.itemref --> Item.id)
KEYREF(inclusion.categoryref --> Category.id)
KEYREF(relate.categoryref --> Category.id)
KEYREF(interest.categoryref --> Category.id)
KEYREF(watch.openauctionref --> OpenAuction.id)
KEYREF(OpenAuction.sell.personref --> Person.id)
KEYREF(bid.personref --> Person.id)
KEYREF(buy.personref --> Person.id)
KEYREF(ClosedAuction.sell.personref --> Person.id)