An Explained UMLi Model

The Cancel (1) and ResultValues (2) InteractionClasses are abstract concepts. Indeed,  user interface diagrams specify essential properties of interaction classes. Thus, Cancel is an ActionInvoker responsible for receiving information from users in form of events. Further, ResultValues is a Displayer responsible for sending visual information to users. Structurally, user interface diagrams describe how InteractionClasses compose user interfaces, i.e., the SearchBook user interface. A domain object of type QueryResult has information to be visualised via ResultValues, as described in the activity diagram.