When creating a use-case diagram, how do i create sub cases that only one actor can use. For example, we have a student information system that students and enrollment admin use. Both will interact with the base use-cases of maintaining student records and maintaining course records. But only the admin can alter information in both of those. Should I add a case for adding and modifying info and then extend it to the two cases or do I draw association to the base cases and some how clarify the extension from there is only for admin?