Challenges For Designing Tangible Systems Torben Wallbaum1 , Andrii Matviienko1 , Wilko Heuten1 , Susanne Boll2 1 OFFIS - Institute for IT 2 University of Oldenburg  Oldenburg, Germany Oldenburg, Germany firstname.lastname @offis.de susanne.boll@uol.de ABSTRACT Scalability Since the introduction of tangible systems and tangible inter- Designers of new tangible systems are often trying to maxi- action a lot of work has been done in this area. The focus for mize the scalability of a system they are developing. In some most of these works was on a success of tangible interaction cases this is needed to enable the use of the system by multiple and few papers discuss when tangible systems fail. In this pa- users or to integrate different modalities into an artifact. How- per, we aim to understand what we can learn from the failures ever, the level of a scalability is still limited in comparison to of tangible systems. We discuss the challenges raised during a smartphone application, and often increases the complexity the design of tangible systems and present a list of research of a tangible system. Couture et al. [3], for example, studied questions for future exploration. whether a tool with a generic form factor can be scaled and sub- stitute tools with a dedicated functionality. However, systems that support an extension of contacts [5, 20], different kinds of INTRODUCTION notifications [1] or modalities [8] still have an extension limit. Tangible interaction has been a widely researched area since The questions that are raised: “What happens if the number of the work by Ishii and Ullmer [9]. During this period of time communication partners increases to 100?" or “What if I have there were both positive and negative experiences with tan- five types of notifications instead of one? Do I want to have gible systems. Hornecker and Buur [7], for example, have five notification objects on my desk?" Matviienko et al. [11] shown that tangible interaction is engaging and provides a low tried to solve this issue with a tangible modular calendar by threshold for accessing interactive systems. Ishii and Ulmer letting the users assign and reassign a contact to a dedicated [9] showed that tangible systems are successful in facilitat- tangible figure. Even though these artifacts have been devel- ing the smooth transition of attention between foreground and oped with a possible scalability in mind, they are still restricted background tasks, what makes them successful for the increase in comparison to most software systems. The extension of of awareness. Shear and Hornecker [14] provided scenarios tangible systems in comparison to smartphone applications and recommendations regarding the future development of is demanding more resources and is harder to realize in the tangible interaction. While most of the works focus on the late stages of the development process. One of the research positive aspects of tangible interaction, we decided to make questions to explore in the future work would be: “How can a closer look at the negative experiences and problems with we design tangible systems with simplified scalability?" tangible systems and what we can learn from it. Throughout the exploration of related work we were aiming to answer the Acceptability following questions: (1) What is this about tangibility that Acceptability and integration of new tangible systems in peo- makes things work and what not? (2) Till what extend one ple’s environment is another challenging aspect for designers can use tangible interaction? (3) Where does the tangible and developers. Systems which are designed in the form of a interaction fail? flower [20], a tree or a house are not immediately accepted, if at all. Even though people are used to tables and desks To find the answers to these questions, we analyzed existing in their working environments, the artifacts in the form of a tangible systems. As a results, we derived a list of challenges table [19] would require some time for a user to get used to it. from the experiences with tangible systems, which we describe Moreover, people get often attached to specific artifacts from and discuss in detail in the following section. their environment, since they inherit memories from their past [2]. When designing artifacts that replace existing objects, it is important to involve users into the design process or integrate CHALLENGES FOR DESIGNING TANGIBLE SYSTEMS existing objects into the design. In this section we aim to outline some of the problems and challenges which raise during the process of design and in- Users who use portable tangible systems, such as CubeLendar teraction with tangible user interfaces. Based on the previous [12] or Forget-Me-Not [20], often face problems of acceptabil- work and our own experience, we discuss the following as- ity, since taking an object to a location uncommon for the usual pects of tangible systems: (1) scalability, (2) acceptability, interaction might raise social concerns or is annoying to the (3) novelty and complexity of interaction, (4) form factor and users. It is a long process of accepting and adapting to a new context of use and (5) maintenance and complexity. In the tangible artifact in the environment, especially when designed following we discuss in detail each of the aforementioned to be used in various contexts of use. For example, an artifact dimensions. which has been designed for domestic environment might not fit into a workplace. As a consequence, users tend not to use should further not only consider affordances through physical the systems in different context. It affects users’ interaction shape, but also take ergonomics into account, which are espe- with a system and can provide misleading information in field cially important for longer-term usage of systems. This leads experiments. us to another research question: “How can we design tangible systems with a flexible context of use?" Another challenging aspect regarding future tangible system is to investigate the change of interaction with the same function- Maintenance and Complexity ality developed as a mobile application and as a tangible object. Users usually do not face problems using new applications on After all, maintaining tangible systems for research purposes their smartphone, but need time to get used to new tangible is cumbersome in comparison to software applications. When systems. What is missing in tangible objects for increasing such applications fail, a researcher can update the software their acceptability? This leads us to another research question: remotely or provide an exchange device with an updated ap- “Which properties of tangible objects can help increasing users’ plication. When a tangible system fails, one has to either fix acceptance?" the whole system or as in the case with smartphone applica- tion provide a new one. However, building a new tangible Novelty and Complexity of Interaction system as back-up is more time and costs consuming than a Different software applications imply interaction with the pure software application. same physical object, e.g. smartphone or laptop. The in- A tangible system usually consists of a multiple hardware teraction paradigm for software systems is often consistent components. These components have to communicate with due to standards and best design practices. Tangible artifact, each other by exchanging data to ensure that a system works as however, have various form factors. Therefore, a user has one module. The more components are integrated in a tangible to learn an interaction for a specific object and adapt to its system, the higher its complexity, the harder its maintenance. affordances. Ullmer et al. [17, 16, 15], however, tried to Another research question here would be: “How can we design solve this issue by presenting physical interaction elements tangible systems with a simplified maintenance?" which can serve common roles across different tangible sys- tems. Furthermore, physical objects are not mutable, and are CONCLUSION not able to change their physical representation as it would be We presented some of the challenges in the application of possible with digital systems, e.g., change a button state [13], designing and developing new tangible systems from our own undo or a history function [10]. This can be a challenging experience and from other related works. The design and aspect, especially when designing for non-technical users like evaluation of tangible interfaces with users in a realistic en- children or elderlies. To reduce complexity of the interaction vironment can be challenging and requires a lot of attention and to ease the way users are interacting with an artifact, de- by researchers and designers. Although, this is an important signers of tangible systems have to carefully select solutions topic, these challenges rarely get reported or reflected after and involve users as early as possible into the design process. an artifact has been designed and implemented into the field. This might include brainstorming sessions to get insights into This work is far from being conclusive, but rather is meant to users’ needs, low-fi prototyping sessions together with users create starting points for discussion. 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