# When to use a multidimensional relationship in an ERD?

When to use a multidimensional relationship in an ERD? My textbook is in Dutch, and the two paragraphs that explain about multidimensional relationships is too vague and brief. I don't understand when it is applicable to use it, and I can't find any information on this subject on the internet.

My guess is that my textbook is naming the concept different from what it's real name is, since I can't find any information on it. In my textbook it shows the following diagram:

Unfortunately, this is the cardinality notation my textbook and teacher are using, I don't know how it translates to any different notations, but to explain how it works: T = mandatory, O = optionality, n, m, k all mean many.

It works in the opposite direction as most notations: All teachers can teach 0 or many subjects and classes, all subjects are teached 1 to many times by teachers and to classes, all classes are teached 1 to many subjects by 1 to many teachers.

Maybe if someone knows its true name I can do some research on this concept...