Wall-sized displays support group work by allowing several people to work both separately and together. However, whether people interact directly through touch input or indirectly through mouse input can have profound effects on collaboration. We present a study that compares how groups collaborate using either multitouch or multiple mice on a wall-display. Participants used both input methods to work on two tasks: a shared-goal task and a mixed-motive task. Results show differences in participants' awareness in collaborative tasks between the two input methods. The results also help understand the physical constraints touch input set on participants' control of actions in collaborative tasks. We discuss how this influences collaboration. Results also show that touch input did not promote more equal participation than mouse input. We contrast the findings to earlier research on wall-display and tabletop collaboration.

The size of information spaces often exceeds the limits of even the largest displays. This makes navigating such spaces through on-screen interactions demanding. However, if users imagine the information space extending in a plane beyond the display's boundaries, they might be able to use the space beyond the display for input. This paper investigates Off-Limits, an interaction concept extending the input space of a large display into the space beyond the screen through the use of mid-air pointing. We develop and evaluate the concept through three empirical studies in one-dimensional space: First, we explore benefits and limitations of off-screen pointing compared to touch interaction and mid-air on-screen pointing; next, we assess users' accuracy in off-screen pointing to model the distance-to-screen vs. accuracy trade-off; and finally, we show how Off-Limits is further improved by applying that model to the naïve approach. Overall, we found that the final Off-Limits concept provides significant performance benefits over on-screen and touch pointing conditions.

Physical movement plays an important role in interaction with wall-displays. Earlier work on its effect on performance has been inconclusive, however, because movement has not been experimentally controlled. In a first experiment, we controlled participants' ability to physically move in front of a 3-meter wide 24-megapixel wall-display. Participants performed a classification task involving navigation using a zoom-and-pan interface. Results suggest that the ability to move does not increase performance, and that a majority of participants used virtual navigation (i.e., zooming and panning) and little or no physical navigation (i.e., moving their bodies). To isolate the effects of physical and virtual navigation, a second experiment compared conditions where participants could navigate using either only physical movement or only virtual navigation. The second experiment showed that physical movement does benefit performance. The results from the experiments suggest that moving may not be improving performance, depending on the use of virtual navigation.

Word-gesture keyboards enable fast text entry by letting users draw the shape of a word on the input surface. Such keyboards have been used extensively for touch devices, but not in mid-air, even though their fluent gestural input seems well suited for this modality. We present Vulture, a word-gesture keyboard for mid-air operation. Vulture adapts touch based word-gesture algorithms to work in mid-air, projects users' movement onto the display, and uses pinch as a word delimiter. A first 10-session study suggests text-entry rates of 20.6 Words Per Minute (WPM) and finds hand-movement speed to be the primary predictor of WPM. A second study shows that with training on a few phrases, participants do 28.1 WPM, 59% of the text-entry rate of direct touch input. Participants' recall of trained gestures in mid-air was low, suggesting that visual feedback is important but also limits performance. Based on data from the studies, we discuss improvements to Vulture and some alternative designs for mid-air text entry.

Multitouch wall-sized displays afford new forms of collaboration: They can be used up close by several users simultaneously, offer high resolution, and provide sufficient space for intertwining individual and joint work. The difference to displays without these capabilities is not well understood. To better understand the collaboration of groups around high-resolution multitouch wall displays, we conducted an exploratory study. Pairs collaborated on a problem-solving task using a 2.8m × 1.2m multitouch display with 24.8 megapixels. The study examines how participants collaborate; navigate relative to the display and to each other; and interact with and share the display. Participants physically navigated among different parts of the display, switched fluidly between parallel and joint work, and shared the display evenly. The results contrast earlier research that suggests difficulties in sharing and collaborating around wall displays. The study suggests that multitouch wall displays can support different collaboration styles and fluid transitions in group work.

The skyline operator has recently emerged as an alternative to ranking queries. It retrieves a number of potential best options for arbitrary monotone preference functions. The success of this operator in the database community is based on the belief that users benefit from the limited effort required to specify skyline queries compared to, for instance, ranking. While application examples of the skyline operator exist, there is no principled analysis of its benefits and limitations in data retrieval tasks. Our study investigates the degree to which users understand skyline queries, how they specify query parameters and how they interact with skyline results made available in listings or map-based interfaces.

In controlled experiments on the relation of display size (i.e., the number of pixels) and the usability of visualizations, the size of the information space can either be kept constant or varied relative to display size. Both experimental approaches have limitations. If the information space is kept constant then the scale ratio between an overview of the entire information space and the lowest zoom level varies, which can impact performance; if the information space is varied then the scale ratio is kept constant, but performance cannot be directly compared. In other words, display size, information space, and scale ratio are interrelated variables. We investigate this relation in two experiments with interfaces that implement classic information visualization techniques-focus+context, overview+detail, and zooming-for multi-scale navigation in maps. Display size varied between 0.17, 1.5, and 13.8 megapixels. Information space varied relative to display size in one experiment and was constant in the other. Results suggest that for tasks where users navigate targets that are visible at all map scales the interfaces do not benefit from a large display: With a constant map size, a larger display does not improve performance with the interfaces; with map size varied relative to display size, participants found interfaces harder to use with a larger display and task completion times decrease only when they are normalized to compensate for the increase in map size. The two experimental approaches show different interaction effects between display size and interface. In particular, focus+context performs relatively worse at a large display size with variable map size, and relatively worse at a small display size with a fixed map size. Based on a theoretical analysis of the interaction with the visualization techniques, we examine individual task actions empirically so as to understand the relative impact of display size and scale ratio on the visualization techniques' performance and to discuss differences between the two experimental approaches.

People typically interact with information visualizations using a mouse. Their physical movement, orientation, and distance to visualizations are rarely used as input. We explore how to use such spatial relations among people and visualizations (i.e., proxemics) to drive interaction with visualizations, focusing here on the spatial relations between a single user and visualizations on a large display. We implement interaction techniques that zoom and pan, query and relate, and adapt visualizations based on tracking of users' position in relation to a large high-resolution display. Alternative prototypes are tested in three user studies and compared with baseline conditions that use a mouse. Our aim is to gain empirical data on the usefulness of a range of design possibilities and to generate more ideas. Among other things, the results show promise for changing zoom level or visual representation with the user's physical distance to a large display. We discuss possible benefits and potential issues to avoid when designing information visualizations that use proxemics.

Whereas the literature is clear on the benefits of large displays and visualizations, little is known about their combination, that is, how display size affect the usability of visualizations. We describe a controlled experiment where 19 participants used focus+context, overview+detail, and zooming techniques with varying display sizes (13.8, 1.5, and 0.17 megapixels). Participants navigated geographical maps to find specific locations, compare items, and follow routes. Results show that for multi-scale navigation, classic interactive visualization techniques did not benefit from being scaled to a large display: In contrast to the literature we find similar performance on medium and large displays. Across display sizes, overview+detail works the best, in particular for comparing items. Focus+context is relatively more difficult to use at a small display size. We explain these findings and discuss the design of interactive visualization techniques for large displays.

Information visualizations have been shown useful in numerous laboratory studies, but their adoption and use in real-life tasks are curiously under-researched. We present a field study of ten programmers who work with an editor extended with a fisheye view of source code. The study triangulates multiple methods (experience sampling, logging, thinking aloud, and interviews) to describe how the visualization is adopted and used. At the concrete level, our results suggest that the visualization was used as frequently as other tools in the programming environment. We also propose extensions to the interface and discuss features that were not used in practice. At the methodological level, the study identifies contributions distinct to individual methods and to their combination, and discusses the relative benefits of laboratory studies and field studies for the evaluation of information visualizations.

Navigating and understanding the source code of a program are highly challenging activities. This paper introduces a fisheye view of source code to a Java programming environment. The fisheye view aims to support a programmer's navigation and understanding by displaying those parts of the source code that have the highest degree of interest given the current focus. An experiment was conducted which compared the usability of the fisheye view with a common, linear presentation of source code. Sixteen participants performed tasks significantly faster with the fisheye view, although results varied dependent on the task type. The participants generally preferred the interface with the fisheye view. We analyse participants' interaction with the fisheye view and suggest how to improve its performance. In the calculation of the degree of interest, we suggest to emphasize those parts of the source code that are semantically related to the programmer's current focus.