Using affinity diagramming as an example, we investigate reality-based interfaces for supporting creative group work. Based on an observational study grounded in the realitybased interaction framework, we identified power vs. reality tradeoffs that can be addressed to find a close fit to embodied practice. Using this knowledge, we designed and implemented a digital workspace for supporting affinity diagramming. Its hybrid interaction techniques combine digital pen & paper with an interactive table and tangible tokens. An additional vertical display is used to support reflection-in-action and for enhancing discussion and coordination. A preliminary user study confirmed the applicability of our tradeoffs and the general acceptance of the tool design.

Abstract. Using affinity diagramming as an example, we investigate interaction techniques for supporting collaborative design activities. Based on an observational study, we identified design guidelines that need to be addressed to find a close fit to embodied practice. Using this knowledge, we designed and implemented AffinityTable, a hybrid surface for supporting affinity diagramming. The tool combines digital pen & paper with an interactive table and tangible tokens. An additional vertical display is used to support reflection and group coordination.

In this paper we describe an experimental study investigating the use of bimanual and multi-finger input for grouping items spatially on a tabletop interface. In a singleuser setup, we compared two typical interaction techniques supporting this task. We studied the grouping and regrouping performance in general and the use of bimanual and multi-finger input in particular. Our results show that the traditional container concept may not be an adequate fit for interactive tabletops. Rather, we demonstrate that informal and organic spatial metaphors are able to harness more benefits of multi-finger and bimanual interaction. We conclude with recommendations for the design of grouping techniques on interactive surfaces.

Figure 1. Tracs is a dual-sided transparency-controlled see-through display system to avoid visual interference on transparent displays and to support fast switching between personal work and collaboration. Users can control the transparency of specific parts of the display (left) or overall (right). ABSTRACTWe present Tracs, a dual-sided see-through display system with controllable transparency. Traditional displays are a constant visual and communication barrier, hindering fast and efficient collaboration of spatially close or facing coworkers. Transparent displays could potentially remove these barriers, but introduce new issues of personal privacy, screen content privacy and visual interference. We therefore propose a solution with controllable transparency to overcome these problems. Tracs consists of two see-through displays, with a transparency-control layer, a backlight layer and a polarization adjustment layer in-between. The transparencycontrol layer is built as a grid of individually addressable transparency-controlled patches, allowing users to control the transparency overall or just locally. Additionally, the locally switchable backlight layer improves the contrast of LCD screen content. Tracs allows users to switch between personal and collaborative work fast and easily and gives them full control of transparent regions on their display.

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