When you are configuring an Advanced Association between two normal classes, you must create a third, normal class used to associate the two other classes. For example: If class A and class B need to be associated with each other, you must create a normal class to create an Advanced Association (named AXB). The X in the name denotes that this class will be used for an association. The class on either side of the X are the classes being associated.
If you are configuring an Advanced Association to create associations between objects of the same class, you must create the normal class and an additional normal class to associate the objects. For example: If class C need to be associated to itself, you must create a normal class to create an Advanced Association (named CXC). The X in the name denotes that this class will be used for an association. The class on either side of the X is the class being associated with itself.