This paper addresses issues of user interface design, relating to ease of use, of handheld CSCW. In particular, we are concerned with the requirements that arise from situations in which a traditionally designed mobile computer with a small keyboard and screen, may not be easily used. This applies to many mobile use contexts, such as inspection work and engineering in the field. By examining two such settings, we assert that what is usually pointed to as severe shortcomings of mobile computing today, for example: awkward keyboard, small display and unreliable networks, are really implications from a conceptual HCI design that emphasise unstructured, unlimited input; a rich, continuous visual feedback channel and marginal use of sound. We introduce MOTILE, a small prototype that demonstrates some alternative ideas about HCI for mobile devices. We suggest that identifying complementing user interface paradigms for handheld CSCW may enhance our understanding not only of mobile computing o...

Many traditional techniques for “looking inside” volumetric data involve removing portions of the data, for example using various cutting tools, to reveal the interior. This allows the user to see hidden parts of the data, but has the disadvantage of removing potentially important surrounding contextual information. We explore an alternate strategy for browsing that uses deformations, where the user can cut into and open up, spread apart, or peel away parts of the volume in real time, making the interior visible while still retaining surrounding context. We consider various deformation strategies and present a number of interaction techniques based on different metaphors. Our designs pay special attention to the semantic layers that might compose a volume (e.g. the skin, muscle, bone in a scan of a human). Users can apply deformations to only selected layers, or apply a given deformation to a different degree to each layer, making browsing more flexible and facilitating the visualization of relationships between layers. Our interaction techniques are controlled with direct, “in place” manipulation, using pop-up menus and 3D widgets, to avoid the divided attention and awkwardness that would come with panels of traditional widgets. Initial user feedback indicates that our techniques are valuable, especially for showing portions of the data spatially situated in context with surrounding data.

We investigate the differences- in terms of both quantitative performance and subjective preference- between direct-touch and mouse input for unimanual and bimanual tasks on tabletop displays. The results of two experiments show that for bimanual tasks performed on tabletops, users benefit from direct-touch input. However, our results also indicate that mouse input may be more appropriate for a single user working on tabletop tasks requiring only single-point interaction.

We present experimental work which explores how the match (or mismatch) between the input space of the hands and the output space of a graphical display influences twohanded input performance. During interaction with computers, a direct correspondence between the input and output spaces is often lacking. Not only are the hands disjoint from the display space, but the reference frames of the hands may in fact be disjoint from one another if two separate input devices (e.g. two mice) are used for twohanded input. In general, we refer to the workspace and origin within which the hands operate as kinesthetic reference frames. Our goal is to better understand how an interface designer's choice of kinesthetic reference frames influences a user’s ability to coordinate two-handed movements, and to explore how the answer to this question may depend on the availability of visual feedback. Understanding this issue has implications for the design of two-handed interaction techniques and input devices, as well as for the reference principle of Guiard’s Kinematic Chain model of human bimanual action. Our results suggest that the Guiard reference principle is robust with respect to variances in the kinesthetic reference frames as long as appropriate visual feedback is present.

We present experimental work that explores the factors governing symmetric bimanual interaction in a two-handed task that requires the user to track a pair of targets, one target with each hand. A symmetric bimanual task is a twohanded task in which each hand is assigned an identical role. In this context, we explore three main experimental factors. We vary the distance between the pair of targets to track: as the targets become further apart, visual diversion increases, forcing the user to divide attention between the two targets. We also vary the demands of the task by using both a slow and a fast tracking speed. Finally, we explore visual integration of sub-tasks: in one condition, the two targets to track are connected by a line segment which visually links the targets, while in the other condition there is no connecting line. Our results indicate that all three experimental factors affect the degree of parallelism, which we quantify using a new metric of bimanual parallelism. Howe...

We present an alternate interface for 3D modeling for use on large scale displays. The interface integrates several concepts specifically selected and enhanced for large scale interaction. These include 2D construction planes spatially integrated in a 3D volume, enhanced orthographic views, smooth transitions between 2D and 3D views, tape drawing as the primary curve and line creation technique, visual viewpoint markers, and continuous twohanded interaction.

We performed several experiments using a Personal Digital Assistant (PDA) as an input device in the nondominant hand along with a mouse in the dominant hand. A PDA is a small hand-held palm-size computer like a 3Com Palm Pilot or a Windows CE device. These are becoming widely available and are easily connected to a PC. Results of our experiments indicate that people can accurately and quickly select among a small numbers of buttons on the PDA using the left hand without looking, and that, as predicted, performance does decrease as the number of buttons increases. Homing times to move both hands between the keyboard and devices are only about 10% to 15% slower than times to move a single hand to the mouse, suggesting that acquiring two devices does not cause a large penalty. In an application task, we found that scrolling web pages using buttons or a scroller on the PDA matched the speed of using a mouse with a conventional scroll bar, and beat the best two-handed times reported in an e...

In this paper we investigate the relationship between bimanual (two-handed) manipulation and the cognitive aspects of task integration, divided attention and epistemic action. We explore these relationships by means of an empirical study comparing a bimanual technique versus a unimanual (one-handed) technique for a curve matching task. The bimanual technique was designed on the principle of integrating the visual, conceptual and input device space domain of both hands. We provide evidence that the bimanual technique has better performance than the unimanual technique and, as the task becomes more cognitively demanding, the bimanual technique exhibits even greater performance benefits. We argue that the design principles and performance improvements are applicable to other task domains. Key words: two-handed input, bimanual input, curve editing, task integration, divided attention. 1

. Direct manipulation, which is the dominating "interaction style" for mobile computers, fails to meet the conditions of many mobile use situations. In particular, it demands too much visual attention of the user. We introduce a new, complementing interaction style (and system) for mobile computers, called MOTILE, which addresses three main requirements of interaction with mobile computers: (1) no visual attention needed; (2) structured, tactile input, and; (3) the use of audio feedback. MOTILE relies on only 4 buttons for user input and "hands free" audio for feedback. Keywords: Mobile computers, interaction style, interface design. Introduction In the traditional office setting, the primary work tasks of users are inside the computer. The reason is simple: office work is to a large extent about processing documents, spreadsheets, emails, etc., and those artefacts are inside the computer. In a mobile use context, this is not usually the case. Maintenance workers, sales perso...

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