Timetrees: a branching-time structure for modeling activity and state in the human-computer interface

Abstract

The design and construction of interactive systems with high usability requires a user-centered approach to system development. In order to support such an approach, it is necessary to provide tools and representations reflecting a behavioral view of the interface-a view centered on user activities and the system activities and states perceived by the user. While behavioral representations exist, there is no behavioral mode I of interaction between a user and a system. Such a model is necessary for formalization and extension of existing behavioral representations. This dissertation presents a model of interactive behavior based on the timetree, a novel tree-based structure representing tasks, user actions, system activity, and system and interface state, all within a framework of branching sequential timelines. The model supports formal definitions, operations and abstraction techniques. Three application areas - a formal definition of an existing behavioral notation, connection between a behavioral representation and a formal model of input devices, and techniques for analysis of behavioral specifications - provide examples of the model's utility.