gistfile1.rb

class SuperParent
  include DataMapper::Resource
  property :id,         Serial
  
  has n, :parents
end

class Parent
  include DataMapper::Resource
  property :id,               Serial
  property :super_parent_id,  Integer, :index => true
  property :ord,              Integer, :index => true
  
  has n, :children
  belongs_to :super_parent

  default_scope(:default).update(:order => [:ord.asc])
end

class Child
  include DataMapper::Resource
  property :id,          Serial
  property :parent_id,   Integer, :index => true
  
  belongs_to :parent
  
  # GOT IT! This is what makes it work:
  default_scope(:default).update(:order => [DataMapper::Query::Direction.new(Parent.properties[:ord])], :links => [:parent])
  # Got info from: http://www.mail-archive.com/datamapper@googlegroups.com/msg01310.html
end

# I want to be able to do this, and have it order by the ord attribute on the `parents` table
super_parent_instance.parents.children