Hi all,

I have a question about Invoicing in the ER-Diagram:

In a school which provides courses, and also hire equipment how could I make the invoice-line, since courses would be in the table CourseInstance and Equipment in the table Equipment.
A customer can enrol in a course, which provides equipment.
A customer can hire equipment without enrolling in a course.

I though of using Specialization of the entity Invoice, but not sure...

Any ideias?

Thank you for your time.