1. Demand change: During the project development, the system functions are adjusted according to the demand change, resulting in changes in the original functional modules of the system.

2. Improper design: The design of the system function module diagram designed in the course of topic opening is unreasonable, which leads to the need for further improvement or adjustment in the process of paper writing.

3. Incomplete implementation: There are differences in the implementation of the opening report and the paper writing process, which leads to differences in the functional module diagram.