1_class_variables.rb

require 'rubygems'
require 'active_support'

class Father
  cattr_accessor :name
end

class Son < Father
end

class Daughter < Father
end

Father.name   = 'Martin'
Son.name      = 'Paul'
Daughter.name = 'Laura'

puts Father.name   #=> Laura
puts Son.name      #=> Laura
puts Daughter.name #=> Laura

2_class_inheritable.rb

require 'rubygems'
require 'active_support'

class Father
  class_inheritable_accessor :name
end

class Son < Father
end

class Daughter < Father
end

Father.name   = 'Martin'
Son.name      = 'Paul'
Daughter.name = 'Laura'

puts Father.name   #=> Martin
puts Son.name      #=> Paul
puts Daughter.name #=> Laura