gistfile1.txt

class Myapp
  controller :libaries do
    # ...
  end

  controller :book, :parent => :library do 
    before do 
      @lib = Library.find(params[:library_id] rescue nil
    end

    get :new do
      @book = (@lib || current_account).books.build(params[:book] || {})
      respond(@book)
    end

    post :create do 
      @analysis = (@lib || current_account).books.build(params[:book] || {})
      @analysis.save
      respond(@book, url(:books_index, :library_id => @lib ? @lib.id : nil))
    end
  end
end

# Now my app should responds for the following routings:
# 
# /books, /books/new, etc... and /library/1/books, /library/1/books/new, etc.  
# 
# calling url(:books_index) i should get /books... 
# ... but calling url(:books_index, :library_id => 1) i should get /library/1/books
#
# Of course there should be some additional option in controller for enabling such behaviour (like :shallow => true or smth), eg:

class Myapp
  controller :books, :parent => :library, :shallow => true do 
    # ...
  end
end