personally, i think this is useful when you have objects which are not stored in database, as shown in the database, e.g. temperature, gps location, balance, etc. You might ask then why those are not stored in the database? In the database we only store a value, but if we want to attach useful, relevant methods to that value,

composed_of attr, :class_name => 'AddressableRecord::Address', :converter => :convert, :allow_nil => true,