The papers in this special section focus on systematic approaches to human-machine interface applications. The motivation for this special issue is the growing increase of remote mission management, unmanned aircraft systems, NextGen operations in the U.S. and its Single European Sky Air Traffic Management Research counterparts in Europe, and other similarly integrated systems of systems that include complex human–machine systems with high levels of autonomy and team dynamics that are difficult to understand and analyze. The issue explores key research areas that impact the properties of these systems, which rely on varied degrees of human and machine interactions. The special issue is a result of the continued interest in the formal verification of complex human–machine systems.

In this paper, we highlight the main research directions currently pursued by the investigators for the development of new tools to improve Web accessibility for users with visual disabilities. The overall principle is to create intelligent software agents used to assist visually impaired individuals in accessing complex on-line data organizations (e.g. tables, frame structures) in a meaningful way. Accessibility agents make use of knowledge representation structures (automatically or manually derived) to assist users in developing navigation plans; these are employed to locate given pieces of information or to answer user's desired goals.

An approach to conduct systematic analysis of risk visualization strategies in a homeland missile defense context is presented. The approach consists of three phases which take different perspectives toward characterizing the problems of resource management and allocation for defense against missile attacks. Decision makers in missile defense are supervisory controllers of highly automated and resource-constrained systems. Our approach is suggested as a method to assess the effectiveness of visualization strategies in a dynamic decision environment. The three phases of our approach included a test for subject utility preferences, a text for subject multi-attribute prefences using the Analytic Hierarchy Process (AHP), and a test for subject action selection using a human-in-the-loop simulation test bed. Our approach is proposed to systematically evaluate the effectiveness of multistage decision making strategies against immediate and delayed threats. The alternatives were calculated based on expected cases of lives lost as a result of attacks on defended areas. Implementation of the test bed enabled us to investigate the effect of visualization formats on decision behaviour. Some preliminary results based on a pilot study will be presented. The implications of our study extend beyond missile defense. In a world where catastrophic loss of civilian lives is seen by some as a victory, those entrusted with homeland security must effectively manage limited resources to combat terrorist activities. Effective visualization formats will help to promote decision that are informed with respect to the risks and outcomes.

In this paper, we provide a progress report on the development of technology to support the non-visual navigation of complex HTML and XML structures.

In this article, we describe and analyze the emergence of a scientific discipline, usability science, which bridges basic research in cognition and perception and the design of usable technology. An analogy between usability science and medical science (which bridges basic biological science and medical practice) is discussed, with lessons drawn from the way in which medical practice translates practical problems into basic research and fosters technology transfer from research to technology. The similarities and differences of usability science to selected applied and basic research disciplines-human factors and human-computer interaction (HCI) is also described. The underlying philosophical differences between basic cognitive research and usability science are described as Wundtian structuralism versus Jamesian pragmatism. Finally, issues that usability science is likely to continue to address-presentation of information, user navigation, interaction, learning, and methods-are described with selective reviews of work in graph reading, controlled movement, and method development and validation.

The paper challenges the notion that any Fitts' Law model can be applied generally to human-computer interaction, and proposes instead that applying Fitts' Law requires knowledge of the users' sequence of movements, direction of movement, and typical movement amplitudes as well as target sizes. Two experiments examined a text selection task with sequences of controlled movements (point-click and point-drag). For the point-click sequence, a Fitt's Law model that used the diagonal across the text object in the direction of pointing (rather than the horizontal extent of the text object) as the target size provided the best fit for the pointing time data, whereas for the point-drag sequence, a Fitts' Law model that used the vertical size of the text object as the target size gave the best fit. Dragging times were fitted well by Fitts' Law models that used either the vertical or horizontal size of the terminal character in the text object. Additional results of note were that pointing in the point-click sequence was consistently faster than in the point-drag sequence, and that pointing in either sequence was consistently faster than dragging. The discussion centres around the need to define task characteristics before applying Fitts' Law to an interface design or analysis, analyses of pointing and of dragging, and implications for interface design.

Understanding design models of the human-computer interface (HCI) may produce two types of benefits. First, interface development often requires input from two different types of experts: human factors specialists and software developers. Given the differences in their backgrounds and roles, human factors specialists and software developers may have different cognitive models of the HCI. Yet, they have to communicate about the interface as part of the design process. If they have different models, their interactions are likely to involve a certain amount of miscommunication. Second, the design process in general is likely to be guided by designers' cognitive models of the HCI, as well as by their knowledge of the user, tasks, and system. Designers do not start with a blank slate; rather they begin with a general model of the object they are designing. The author's approach to a design model of the HCI was to have three groups make judgments of categorical similarity about the components of an interface: human factors specialists with HCI design experience, software developers with HCI design experience, and a baseline group of computer users with no experience in HCI design. The components of the user interface included both display components such as windows, text, and graphics, and user interaction concepts, such as command language, editing, and help. The judgments of the three groups were analyzed using hierarchical cluster analysis and Pathfinder. These methods indicated, respectively, how the groups categorized the concepts, and network representations of the concepts for each group. The Pathfinder analysis provides greater information about local, pairwise relations among concepts, whereas the cluster analysis shows global, categorical relations to a greater extent.

Two experiments examined selecting text using a movement sequence of pointing and dragging. Experiment 1 showed that, in the Point-Drag sequence, the pointing time was related to the pointing distance but not to the width of the text to be selected; in contrast, pointing time was related to both the pointing distance and the width of the text in the Point-Click sequence. Experiment 2 demonstrated that both the pointing and dragging times for the Point-Drag sequence were sensitive to the height of the text that was selected. The discussion of the results centers around the application of Fitts' Law to pointing and dragging in a point-drag sequence, proposing that the target for pointing is the leftmost edge of the text to be selected, and the target for dragging is the rightmost edge of the text.

Three models of human interactions with computer-displayed statistical graphics were developed and tested in an experiment which examined users' speed and accuracy on identification and comparison questions using 17 graph types. The results indicated that response time and accuracy were influenced by the perceptual and informational complexity of the graph, as well as the relation between the figure and axes, (Model 1); by the physical elements of the graph — points, lines, and areas (Model 2); and by the data-ink ratio and data density (Model 3). The discussion focuses on the development of a single integrated model of interactions with graphics.

No abstract available.