Adding rails class methods to plugin with ActiveSupport::Concern

includes_active_support_concern.rb

module MyModule
  extend ActiveSupport::Concern

  included do
    #class method defined in ActiveSupport::Validations::ClassMethods (i.e. using ActiveSupport::Concern
    validate :my_validation

    #Rails method defined in ActiveSupport::CoreExt ... 
    cattr_accessor :yo
  end

  attr_accessor :some_instance_var

  def i_am_an_instance_method
   puts "instance method"
  end

  module ClassMethods

   attr_accessor :some_class_var

   def i_am_a_class_method
     puts "class method"
   end
  end

end

instance attr correct?
http://pivotallabs.com/users/mgehard/blog/articles/1369-using-activesupport-concern-for-easy-mix-ins-

http://opensoul.org/blog/archives/2011/02/07/concerning-activesupportconcern/