gistfile1.rb

# This declaration ..
semantic_menu :class => "top_level_nav" do |root|
  root.add "Home", root_path
  root.add "Settings", settings_path do |settings|
    settings.add "Users", users_path, :activate_for_deeper_paths => true
  end
end

# .. would make the "Users" item active for all this URIs

http://localhost:3000/users
http://localhost:3000/users/25
http://localhost:3000/users/new
http://localhost:3000/users/edit/25