A book has several chapters, and each chapter has several sections. This could be deemed as either a two-level tree or a nested list.
Now I need to display the catalogue of the book. And the user can drag-and-drop to re-order chapters and sections. Do you know any good javascript widget for this?
After the re-ordering, the new order needs to be persisted to the database. Could you please give me some hint about how to design the database schema?