This reading is a consequence of the equivalence of an association to an attribute. As an attribute is only the property of an instance, the association end on the target side is also only a property of an instance. Book → Person: A Book is authored by an ordered set of many Persons in the role of author When you read in the other direction, you generally will need to change the verb form from active to passive or vice versa. Person → Book: A Person authors a set of many Books in the roles of myBooks