Bukkit

The Minimum

Diamonds!:
  tasks:
    '0':
      type: collect
      id: 264
      display: Diamond
      amount: 5
  onJoin:
    message: Hey `player! Can you go get my 5 diamonds! I'll pay you $500
  onDrop:
    message: Aww fine I'll go find someone else :(
    money: -50
  onComplete:
    message: Thanks! Now I can feed my lava dragon! ;)
    money: 500

A basic quest consists of 1 task, and events that are set off. The task has a Task Type, a item id/mob name/player name, what that id/name should actually display as in the chat, and an amount to kill/collect.

The onSomethings (onJoin, onDrop, and onComplete) are all interchangeable nodes, meaning they all have the same abilities, and rewards, but are set off at different times. It can have a message, and rewards/fees(also known as effects); like money, health, hunger, items, and even console commands which can extend qQuests to give rewards in different plugins. The money/health/hunger can also be negative which would take the respective thing from the player.