Dennis>> why 4 types of relations are better than one type of relations?
Jiri> Because it better supports human-like thinking. Our mind is working
Jiri> with multiple types of relations on the level where reasoning applies.
Our mind is working with far more than 4 types of relations.
That's why it's not good idea to implement 4 types of relations. In one hand it's too complex. In another hand it's still not enough.
Better approach would be to use one relation which is able to represent all other types of relations.