Interfaces of interactive systems for domestic use are usually designed for individual interactions, although these interactions influence multiple users. In order to prevent conflicts and unforeseen influences on others, we propose to leverage the human ability to take each other into consideration in the interaction. A promising approach for this is found in the social translucence framework, originally described by Erickson & Kellogg. In this paper, we investigate how to design multi-user interfaces for domestic interactive systems, through two design cases where we focus on the implementation of social translucence constructs (visibility, awareness, and accountability) in the interaction. We use the resulting designs to extract design considerations: interfaces should not prescribe behavior, need to offer sufficient interaction alternatives, and previous settings need to be retrievable. We also propose four steps that can be integrated in any design process to help designers in creating interfaces that support multi-user interaction through social translucence.

More and more connected systems are entering the social and shared home environment. Interaction with these systems is often rather individual and based on personal preferences, leading to conflicts in multi-user situations. In this paper, we aim to develop a perspective on how to design for multi-user interaction with connected lighting systems, based on a better understanding of reallife interpersonal lighting conflicts. In order to understand everyday lighting conflicts, including their causes and resolution strategies, we present two studies. First, we observe real-life lighting conflicts between couples living in single-room apartments. Using probes for data gathering followed by dyadic interviews, we identify the role of agreements on use in conflicts and we identify different types of conflicts (preference, activity, and attitude conflicts). Next, we take a more disruptive approach based on technology probes, where we provoke lighting conflicts in family living rooms to observe resolution strategies. We find that people try to avoid conflicts at all costs. If there is a risk that others are negatively affected by an adjustment, people rather not interact with the system at all. Based on these insights, we defined a perspective on designing for multi-user interaction that provides the user with the confidence that interactions are socially accepted. This assurance can be given by presenting the user with information leading to awareness about the acceptance of a lighting change by the other users. We advise on what information can be visualized, based on the three conflict types we observed in the study. The combination of a deeper understanding of conflicts and a perspective on multi-user interface design can serve as a starting point to design better multi-user interfaces for domestic connected systems.

Interfaces are commonly designed from the perspective of individual users, even though most of the systems we use in everyday life are in fact shared. We argue that more attention is needed for system sharing, especially because interfaces are known to influence coordination of shared use. In this work, we aim to deepen the understanding of this relation. To do so, we design three interfaces for a shared lighting system that vary in the type of social information they allow people to share with others and in their overall interaction style. We systematically compare longitudinal and real-life use of the interfaces, evaluating (1) people's appraisal of three types of social information and (2) the influence of an interaction style on coordination of shared use. The results disclose relations between the interface and the amount of verbal communication, consideration, and accountability. With this work, we urge the need for interaction designers to consider shared use.

IoT developments make shared systems, such as lighting systems, increasingly connected. From an interaction perspective, this offers opportunities for personal control. Especially for lighting, the benefits of personal control have been underlined by research. However, how to design interfaces that realise these potential benefits is much less investigated. This paper presents a long-term qualitative study in which three interfaces for a shared lighting system are evaluated by 17 people working in an open plan office. The interfaces are designed to vary on a number of characteristics, including the distribution over space, interaction modality, and sequence of interaction. Based on the results, we provide new insights in the impact of interface characteristics on lighting use and experience. We find, i.a., that having an interface on a personal multipurpose device or on a central interface solely dedicated to lighting, influences whether people make individual or more collective lighting adjustments and decisions.

Most systems that we use in everyday life are shared—because multiple people can interact or because an interaction by one person can affect other people. However, everyday Internet of Things systems are often designed for individual use. Prior research on collaboration technologies (Computer Supported Collaborative Work) has shown that to coordinate system sharing people require awareness of the social context, which interfaces can support by making salient information visible. Although literature exists on how to design for awareness, this can be fragmented and difficult to relate to other application domains. To introduce a broader audience of interaction designers to awareness, we aim to make the available design knowledge more generalizable and operational. With this aim, we construct the Designing for Awareness in Shared Systems framework that gives a structured and comprehensive overview of design considerations for awareness. The framework can stimulate reflection and inform decision-making when designing interactions with shared systems.