Scenario
Design a University Library system with two actors: Student (primary) and Librarian (secondary staff). Students "Borrow Book". Borrowing a book unconditionally «includes» "Check Student Fine Balance". If the student returns a book late during "Return Book", they are optionally triggered to "Pay Overdue Fine" via «extend».
Objective
Build the entire relationship structure using the canvas tools: connect Student, Librarian, Borrow Book, Return Book, Check Fine Balance, and Pay Overdue Fine.