gistfile1.rb

class Game
  include DataMapper::Resource
  
  #
  # Properties
  #
  property :id, Serial
  
  #
  # Associations
  #
  has n, :game_memberships
  has n, :players, :through => :game_memberships

end

class CaptainGame < Game

  has 2, :captains, :through => :players

end

class GameMembership
  include DataMapper::Resource
  
  #
  # Properties
  #
  property :id, Serial

  # 
  # Associations
  #
  belongs_to :game
  belongs_to :player

end

class Player
  include DataMapper::Resource
  #
  # Properties
  #
  property :id,     Serial

  # 
  # Associations
  #
  has n, :game_memberships
  has n, :games, :through => :game_memberships

end