Please add course prerequisites for each courses so that students know which course they have to take before taking a course, Administrator can choose to make prerequisite courses either optional or mandatory.

-If they are optional, students can ignore prerequisites and take a course directly.

-If they are mandatory, students have to finish those prerequisites before taking a course, but students are always allowed to submit some documents to prove that they have already have the prerequisite knowledge from else where.

-Some visual feature like a course requirement tree figure can be implemented so that users can see all the course requirements and the entire course structure of the online community.