CIN does not need to be part of a User class if that's what you are asking.

Imagine that the webapp will be used by Tricia in the CS office. The only "user" of application (i.e. the user who needs to login/logout) is Tricia. If a student wants to borrow something, Tricia will enter the student's CIN and name and check out the item, and that's it. In other words, the students (or the borrowers) do not need to have an account with the application, and the "users" of the application, who are essentially administrators or librarians, do not need to have CIN.