1. User management.

2. Book management.

3. Borrow and return registration.

4. Book inquiry.

Step 5 make a reservation.

6. System settings.

The above is the top level, and each top-level problem can be further subdivided. For example, loan-return registration can be divided into the following issues:

1. Book borrowing registration

2. Book return registration

3. Check the loan situation

4. Overdue fines.

Break down the problem into problems. If an engineer can complete it within a milestone, there is no need to continue decomposition.