Identifying Critical Interaction Scenarios for Innovative User Modeling

Usability testing typically focuses on methodology and metrics, while the specific interactions being tested are chosen in an ad hoc way. This paper demonstrates a framework for organizing interaction scenarios for graphical user interfaces (GUI). The framework is an adaptation of the two-dimensional abstraction hierarchy introduced by Rasmussen [1] in which an interaction consists of a purpose, functionality, and form. Interactions for a GUI are organized into four main categories, with numerous subtasks. The four main categories determined are 1) object manipulation, 2) content manipulation, 3) view manipulation, and 4) information presentation. The general framework can guide evaluators in choosing key interaction scenarios for GUI applications across a diverse array of user capabilities. 1.0 INTRODUCTION Many tools exist to facilitate the evaluation of computer interfaces (e.g., cognitive walkthroughs, heuristic evaluations, user testing, etc.). Ideally these methods would investigate all possible interaction scenarios that might occur in a particular application between the user and the computer. However, this is not realistically feasible. As a result, evaluators often employ only small subsets of interactions or selected representative interactions. To our knowledge no research to date has provided a systematic method to determine what interactions should be investigated, or how interactions could be compared to other interactions within the same interface, or with interactions in other interfaces. A hierarchical framework that organizes potential interaction scenarios would provide support for choosing interactions to be tested, and allow comparison of interactions within and between applications. One difficulty in creating such a framework is that an interface abstracts the user from the task they are trying to accomplish. The interface can be viewed as a “cognitive agent” on which the user must act to accomplish the desired goals [2]. The user’s ultimate goal (e.g., producing a document, creating a chart, coordinating data, etc.) is not directly performed, but instead is composed of a sequence of low-level interactions with the interface. In this regard the “usability” of an interface is a combination of low-level actions (e.g. moving a mouse, pressing a key combination, etc.), the sequence of low-level interactions required to accomplish a goal, and the ability of the interface to satisfy the user’s goal. These different aspects of the task reflect both physical and cognitive behavior from the user. Additionally, interactions can be initiated by the interface (e.g. providing feedback, alerting the user to system status, etc.), further complicating efforts to create a general framework of interactions. For a high level goal, such as inserting a chart into a document, there are a number of lower level objectives that must be accomplished, typically by performing actions on objects through the functionality of the interface. This structure, characterized by purpose at the higher levels, functional aspects in the middle levels, and form at the lower levels, can be represented as an abstraction hierarchy. This type of hierarchy, applied to interactions in a graphical user interface (GUI) can elicit key interaction scenarios. In the succeeding sections, a description of the general framework is followed by an example of how it may be applied. 2.0 ABSTRACTION HIERARCHY Rasmussen’s abstraction hierarchy [3] serves as the foundation for the framework and possesses two dimensions, as shown in Figure 1. On the horizontal axis is decomposition, where moving to the right can be considered “zooming in” on components of the system. On the vertical axis is the level of abstraction, which breaks down the task, from goals or purposes at the highest level down through the physical form of the interface at the other. Goals propagate down through the hierarchy, eventually affecting the physical functioning of the system, while the physical form can produce effects that propagate up the hierarchy, and can affect the purposes, either by confounding them, or creating new purposes. General Category Category Subtasks Specific Subtasks