How to Structure Multiple Levels of Hierarchy in Ruby on Rails?

A rails app contains many different Pages of content. The Pages are organized into small groups known as Sections: ``` class Page < ActiveRecord::Base attr_accessible: section_id #etc.. belongs_to :section end class Section < ActiveRecord::Base attr_accessible :title #, etc... has_many :pages end ``` The Sections need to be organized too, but what is the best way to do this - re-use sections themselves, or create a new Unit model? Option 1 - Re-use Section Allow Section to have children and parent Sections. That way, you don't need to create another model with similar fields as Section. Some sections will have_many pages, and other sections will have_many children sections: ``` class Section < ActiveRecord::Base attr_accessible :parent_id :title # etc... has_many :pages belongs_to :parent, class_name: "Section" has_many :children, class_name: "Section", foreign_key: "parent_id" end ``` Option 2 - new Unit model Create another model called Unit to organize the sections. It will have many similar fields to section, but it will be a clearly separate entity. ``` class Section < ActiveRecord::Base attr_accessible :title, :unit_id # etc... has_many :pages belongs_to :units end class Unit < ActiveRecord::Base attr_accessible :title # etc... has_many :sections end ``` The advantage of Option 1 is it avoid some duplication, and could be adapted in the future if even more levels are needed. However, Option 2 clearly separates the roles of Sections, which have_many pages, from Units, which have_many Sections, which can help keep other code clear. Which is the best approach? Update It seems Option 2 would have clearer code, such as when going through all the Sections. Is it worth re-using Sections if it would make some code more complicated? For example, here's how to list all the Sections in an organized manner: Option 2 - For each Unit, list all the child sections. Then list any Sections that aren't in any Unit. Option 1 - For each parent Section, list all the children Sections. Then list any Section that has with no parent Section or child Section.