Digital Mysteries is a collaborative learning tool used by a small group of students working around a digital tabletop. This group of students is usually supervised, and possibly assessed, by a teacher. The elements involved in this case include the students, the tabletop, and the teacher. The desired outcome is not just the final solution of the problem, but also the building of knowledge during the process. To inform the design of such a complex system, it is not possible to think in terms of traditional HCI design guidelines, or even digital tabletop design guidelines as these mostly focus on the interaction aspects of the design and overlook the cognitive, social, and organizational aspects that are involved (Rogers and Ellis, 1994). Looking at this system from the perspective of distributed cognition theory (described in Section 1.3.2) (Hollan et al., 2000; Rogers and Ellis, 1994; Norman, 1993; Halverson, 2002; Nardi, 1995), on the other hand, brings into focus the functional system, its inputs and outputs, the intermediate representational forms, the goal and background of the activity, the available resources, and any environmental factors that contribute to the accomplishment of the task (Perry, 2003). When designing a system for a classroom, we cannot realistically control the people or the environment, but we can control the elements of the resources that include the tools, and the representation states involved. The aim is that with a good design, the system will positively affect the people and the work environment leading to better interactions and enhanced learning. Distributed cognition theory (DC) was therefore used to guide the design and evaluation of Digital Mysteries. Halverson (2002) highlighted the weak descriptive power of DC, compared to such theories as activity theory, which limits its rhetorical force when used to communicate a work setting or an implementation that is guided by the theory. He also highlighted the difficulty in applying the theory to actual settings. Therefore, even thought the effect of DC on the design of Digital Mysteries might not be very clear, its underlying concepts motivated different aspects of the design and evaluation of the application. Among the aspects of DC that had direct influence on the design are
• Making use of the concepts of externalization, representation states, and cognitive tools to think of how it is possible to design tools that encourage students to externalize their thinking into persistent representations states that are more accessible to external observes, and that can be logged by the system.
• The importance of utilizing the space, in this case the tabletop surface, to share the cog- nitive load. As discussed in Section 2.2.1.1, the space can be used to simplify perception, choice, and internal calculations, and also to structure and mediate collaboration. There- fore, DC highlights the importance that the persistent representations states be ones that are manipulable on the table surface.
• The importance of looking beyond the tangible outcomes of the process, and to look at the verbal and non-verbal behaviour of the people involved during the process as an important
part in the collaborative process (verbal and non-verbal behaviour of people around tables from a DC perspective is discussed in Section 2.2.2). Maintaining barrier-free visual and verbal communication channels, and allowing students the freedom of movement around the table, were therefore other main design goals of Digital Mysteries.
The concepts of cognitive tools and representation states had direct implications on the design of Digital Mysteries and are therefore discussed in more details below.
5.4.1 The Tools
Digital Mysteries was developed for a top-projected prototype, multi-pen, horizontal Promethean Activboard (1024×768resolution) specially developed for the application. Activboard uses a solid front projection surface which students can (and do) safely lean on, giving it many of the physical affordances of a real table. The board reacts to three battery-free pens that look and feel like normal whiteboard pens. The two principal physical tools involved in Digital Mysteries are the table and the pens. In designing the application we anticipated its use on either a pen-based or a touch-based platforms. Consequently, for the pen-based Activboard we focused on maintaining direct touch interaction and the use of an interaction technique suitable for both pen-based and touch-based input.
The social affordances of traditional tables as outlined in Section 1.4.1 underpin the collab- orative learning environment. These affordances establish the conditions for effective learning activities, including conversation and argument, by allowing people to have fluid, face-to-face, barrier free communication. The horizontal surface of the table allows physical support and pro- vides a space that can be used to reduce cognitive load (Hollan et al., 2000). Moreover, tables allow people to use the surface to structure and mediate group collaboration (Tang, 1991; Kruger et al., 2003; Scott et al., 2004). Implementing Digital Mysteries in a traditional computer setting whether using a desktop computer, an interactive whiteboard, or even a network based solution means sacrificing many or all of these qualities. The unique advantage of digital tabletops is that they maintain many of the benefits of traditional tables, yet allow for the addition of digital func- tionalities afforded by traditional desktop settings, such as structuring the task, logging, and feed- back, in addition to digital functionalities afforded only by tabletops such as multi-synchronous input and direct-touch interaction (see Section 1.4.2). As well as the pen and table as physical tools, the design of Digital Mysteries uses a number of virtual tools (e.g. grouping, post-it note, and sticky tape tools) to satisfy the design goal of externalization (these are discussed in detail in the following sections).
5.4.2 Representation states
The approach used by DC to understand interactions between people and technology is to study the transformations of representation states during the process. DC places a clear emphasis on
representation states and their importance to cognition. Representation states are not necessarily bound to material objects, but may be mental representations, audio representations expressed in conversation, or physical movements such as gestures. Representation states are transformed by tools. Thus a mental representation may be transformed into a written note on a piece of paper. The concept of cognitive tools, and how they can be used to make mental representations accessible to interpretations, played a significant role in shaping the design of the externalization tools for Digital Mysteries.