Interactions based on the DiamondTouch

TheDiamondTouch[DL01] system is particular noteworthy because it is capable of distinguish- ing input from multiple users reliably which is a feature no other important hardware platform

2.2 Tabletop Interaction Techniques 17

supports. Also the system has been used in many academic studies and therefore plays an impor- tant role in forming our understanding of tabletop usage and interaction. However, the system enforces a particular interaction style because, in its unmodified state, it reports relatively little information upon contact. The limitation to an axis-aligned bounding box per user (potentially stemming from multiple fingers) does not allow for the same flexibility in input interpretation and therefore user interaction that other systems could provide. Because of these limitations many applications developed for theDiamondTouchplatform feature an interaction style that could be described as an extension to the traditional WIMP paradigm. Interaction happens mostly through one single finger tip and is often restricted to 2D pointing, selection and movement.

Ryall, Forlines, Shen and Morris investigated the effect of group and table size on collabo- rative performance. The experiments were conducted on two differently sized interactive tables. Group size and its effects on task performance was also studied. Groups of two or four par- ticipants had to assemble a poem from individual tiles. While no significant effect was found between thetable sizes, larger groups were faster than smaller groups. Furthermore, participants reported a strong personal preference for the larger table size andfeltas if they completed the task faster. A variety of implications for resource management and social interactions (e.g., level of individual participation, conflict resolution) are reported. An interesting finding was that where

work resources are displayed influenced work strategies adopted by groups which has strong im- plications for the design of applications for group collaboration. For larger groups additional vertical displays might be beneficial especially in data intensive tasks.

Because of the unique user identification capabilities the platform has been utilized to study techniques that depend or enforceobject ownership.

Transitioning from individual to group work is a common practice in collaborative work. This practice often involves the passing on of work resources to other collaborators or releasing re- sources to the entire group. Ringel et al. [RRS+04] present and study several interaction tech- niques that ease the transition of ownership status between group members or from private to public accessibility. Their “relocate” technique was more efficient and also was preferred over the “resize”, “reorient” and “release” techniques. In this technique ownership is associated and enforced via special areas on the tabletop display reserved for private or shared use.

In a later publication [RMRS+04] more general coordination strategies and issues are observed and discussed. Based on these observations a set of techniques is discussed to improve group collaboration interfaces through a “coordination policies” framework.

With SIDES [POMW06] Piper et al. present and study ways to help adolescents with As- perger’s Syndrome practice effective group work skills using a multi-player interactive tabletop game. The findings indicate that cooperative tabletop computer games can be engaging and may support the acquisition of effective group work strategies among individuals with special needs - in particular when the hardware can identify who is interacting. Also several design lessons to inform the development of similar systems are discussed.

Morris, Paepcke and Winograd [MPW06] present inTeamSearch ways to specify boolean search queries either collaboratively or concurrently using meta information and query tokens. A study investigated whether queries constructed via a group effort or performed individually are more efficient (i.e., faster, better results). The results did not show significant efficiency benefits

18 2. Related Work

for the group effort, but that collective query formation has advantages in terms of enhancing group collaboration and awareness, suggesting that group centric UIs may offer other benefits beyond the efficiency and result quality usually accredited to them.

TeamTag [MPWS06] uses a slightly modified interface to support bio-diversity researchers in classifying photographs of different animals. Tags may be applied by first touching the appropri- ate category and then the photograph to be tagged. Of research interest was whether participants would prefer centralized or replicated controls. Users showed a clear preference for the replicated controls albeit no efficiency benefits could be found.

ThePersonal Digital Historian[SLM+01,SLV03] is a photo sharing application specifically targeted at co-located sharing of photographs and story-telling. The system supports users in constructing narrations from a vast database of digital pictures by providing different views onto the image collection. The different layouts are organized along the four “W’s” of storytelling; where, when, who and what. While many interesting information presentation and interface aspects for co-located group ware are introduced and discussed the interaction techniques are mostly limited to point and click interactions.

Forlines and Shen [FS05] present inDTLensinteraction techniques to enable multiple users to interact simultaneously with geo-spatial data such as multi-layered maps. Users may create magnifying lenses by touching the display with two fingers. The size of the lens is identical to the bounding box reported by the hardware. Several interaction techniques are available to reposition and resize the lenses or change its zoom level. The system takes advantage of the user identifying hardware to mitigate interaction conflicts. Lens parameters may only be adjusted by the creator of the lens greatly easing transitions between individual and group work.

Wigdor et al. [WPR+07] report findings from a long term case study of one individual user performing his everyday office work tasks on an interactive tabletop. Relatively few differ- ences in interaction style were found in comparison to a standard PC (not surprisingly since the tabletop was used to drive a standard MS Windows environment). However, some actions were performed using both hands. In most observed cases of bi-manualism the user applied this strat- egy to increase his reach and therefore optimize task performance, an interesting finding because many research articles speculate about the particular suitability of tabletop systems to support bi-manual interaction for complexer interaction styles. Some findings impacting ergonomics are offered. The user clearly preferred his tabletop mounted angled toward him but had the con- flicting requirement for dual use of the device as storage space for desk clutter and sometimes meeting venue. Finally text input issues regarding the usage of a software on-screen keyboard are highlighted.

Shen et al. [SRF+06] summarize findings from various projects implemented on the Dia- mondTouchand suggests guidelines informing the design of direct-touch tabletops. An ex- tensive set of informal observations complemented by results from controlled user studies are used to illustrate these guidelines. Furthermore, the authors stress the importance of interaction techniques specifically designed for tabletop interaction rather than simple adaptation of mouse and keyboard based interaction techniques.

Although many exciting application scenarios for digital tabletops have been explored it is still not entirely clear what might be the “killer application” for digital tabletops. However, in

2.2 Tabletop Interaction Techniques 19

the end this might not be an overly important question – if we look back at the reasons for adaption and life-cycles of other technologies it can be said that many needed to go through several iterations and refinements before they were ready for the mass market (e.g., the mouse was invented in the 60s but only became widespread in the late 80s). It appears that multi-touch tabletops are not a platform that lends itself toward a simple extension of the desktop computing paradigm but an entirely independent class of devices best suited for special purpose applications. We would further argue that for the time being tabletop computing should still be considered as a discipline in its infancy. If we accept this precondition we should also be willing – and trying – to openly think about every aspect of the domain (and potentially question it). Therefore, we will concentrate our discussion of related work, but also our own explorations later on, on aspects that determine how we interact with the virtual realm. This inevitably shifts the focus away from applications and application specific design decisions towards more low level questions of how to move and otherwise manipulate on-screen objects.