class Category < ActiveRecord::Base has_and_belongs_to_many :posts has_and_belongs_to_many :special_posts, :class_name => "Post" has_and_belongs_to_many :other_posts, :class_name => "Post" def self.what_are_you 'a category...' end has_many :categorizations has_many :authors, :through => :categorizations, :select => 'authors.*, categorizations.post_id' end class SpecialCategory < Category def self.what_are_you 'a special category...' end end