16.15. Qualified Association
A qualified association has a qualifier that is used to select an object (or objects) from a larger set of related objects, based upon the qualifier key. Informally, in a software perspective, it suggests looking things up by a key, such as objects in a HashMap . For example, if a ProductCatalog contains many ProductDescriptions , and each one can be selected by an itemID , then the UML notation in Figure 16.15 can be used to depict this.