[Zope] Relations between objects in zope?

Hi there all, For a project to learn working with Zope I want to use relations between several zope objects. for instance. I have a trainee form. On this form I create a new course for people to take. This course has some prerequisites. Somehow I want to link this new course to the 'old' courses in the system. With mysql i just create a new table call it course to preq and fil it with the usefull stuf. But in zope I dont have ... clue how to accomplish this task. Do i need to fall back by using an Relational Database like Mysql OR can I achieve this with Zope? Yours sincerely, J.somhorst