我们希望按如下url来查看articles archive:
http://localhost/articles
http://localhost/articles/2007
http://localhost/articles/2007/9
http://localhost/articles/2007/9/28
我们可以这样定义routes:

# in routes.rb
map.connect 'articles/:year/:month/:day', :controller => 'articles',
  :month => nil, :day => nil, :requirements => { :year => /\d{4}/ }