###############strom cez 3 tabulky
class Document < ActiveRecord::Base
  has_many :sections
  has_many :paragraphs, :through => :sections
end

class Section < ActiveRecord::Base
  belongs_to :document
  has_many :paragraphs
end

class Paragraph < ActiveRecord::Base
  belongs_to :section
end

################strom cez 4 tabulky
class Document < ActiveRecord::Base
  has_many :sections
  has_many :paragraphs, :through => :sections
end

class Section < ActiveRecord::Base
  belongs_to :document
  has_many :paragraphs
end

class Paragraph < ActiveRecord::Base
  belongs_to :section
  has_many :xyzs
end

class Xyz < ActiveRecord::Base
  belongs_to :paragraph
end