Multi-Valued Reference Properties

Collection types for properties

By default, a non-functional association end connects a set of instances in the target class to any instance of the source class. This means that the collection values of the corresponding multi-valued reference property are sets. However, there are also cases in which a non-functional association end is ordered, and consequently, the collection values of the corresponding multi-valued reference property take the form of ordered sets.

In the following example, the publishedBooks association end is not ordered, while the authors association end is ordered since the order of the authors of a book is important. Notice that in a UML class diagram, an ordered association end is marked up with the annotation {ordered}.