Notational Techniques for Accommodating User Intention Shifts

Good user interface designs allow for user intention shifts. The asynchronous nature of direct maniulation interfaces inherently demands consideration of user intention shifts during the performance of a task. Maintaining a focus on the primary function of a task while at the same time accommodating user intention shifts is difficult for interface designers when both these aspects are represented at the same design level. The User Action Notation (UAN), a technique for representing asynchronous interfaces, contains a mechanism for specifying points in a task where user intention shifts may occur. A complementary technique, Task Transition Diagrams (TTDs), is used to specify tasks that users can perform to interrupt their current task. The Task Transition Diagram is a notation that allows a designer to map out the set of tasks and intentions of users without having to be concerned with the minutiae of how a user accomplishes those tasks.