admin.rb

class Admin < Person
  include Log
  watch_for_log :bar
end

gistfile2.txt

Person.log_attributes --> ["foo"]
Admin.log_attributes --> ["foo", "bar"]
Person.log_attributes --> ["foo"]

log.rb

module Log
    def self.included(base)
      base.extend(Log::ClassMethods)
    end

    module ClassMethods
      base.attr_reader :log_attributes
      def watch_for_log(*args)
        @log_attributes ||= []
        @log_attributes += args.collect(&:to_s)
        @log_attributes += superclass.log_attributes if superclass.respond_to?(:log_attributes)
        @log_attributes.uniq!
      end

    end
end

person.rb

class Person
  include Log
  watch_for_log :foo
end