Each project is managed by one department, and a department may manage many projects. Instructors may take a special loan of textbooks for courses that they teach. More than one instructor can be assigned to a course, and more than one textbook can be used in each course. The books are assigned to the course, and an instructor always gets a special loan of all the books assigned to each course that he or she teaches. An instructor may also obtain a special loan of books other than those assigned to courses taught by that instructor.
Instructors obtain a special loan of only some of the books assigned to a course.
A library system contains libraries, books, authors, and patrons with key attributes libno, bookno, authno, and patno respectively. A library can hold many copies of a book, and a book can appear in many libraries. A book and a library enter into a relationship grouping by sharing a copy. This relationship instance has a cost attribute, which states how much the library paid for the book. When a patron borrows a book, the transaction creates an instance of the patron-book relationship and attaches a duedate attribute to it.