class Subtask
  include DataMapper::Resource

  property :id, Serial, :nullable => false
  property :description, String, :nullable => false
  property :type, Discriminator, :nullable => false

  # Abstract
  def initialize (*params)
    raise NotImplementedError, "Subtask is abstract!" if self.class == Subtask
    super
  end
end

class TextTask < Subtask
end

class ImageTask < Subtask
  property :submissions, Integer, :nullable => false
  property :someunique_id, Integer, :unique_index => true
end