A Taxonomy of Ambient Information Systems: Four Patterns of Design Zachary Pousman College of Computing/GVU Center Georgia Institute of Technology Atlanta, GA 30332 +1 (404) 385-2447 zach@cc.gatech.edu John Stasko College of Computing/GVU Center Georgia Institute of Technology Atlanta, GA 30332 + 1 (404) 894 5617 stasko@cc.gatech.edu ABSTRACT Researchers have explored the design of ambient information systems across a wide range of physical and screen-based media. This work has yielded rich examples of design approaches to the problem of presenting information about a user���s world in a way that is not distracting, but is aesthetically pleasing, and tangible to varying degrees. Despite these successes, accumulating theoretical and craft knowledge has been stymied by the lack of a unified vocabulary to describe these systems and a consequent lack of a framework for understanding their design attributes. We argue that this area would significantly benefit from consensus about the design space of ambient information systems and the design attributes that define and distinguish existing approaches. We present a definition of ambient information systems and a taxonomy across four design dimensions: Information Capacity, Notification Level, Representational Fidelity, and Aesthetic Emphasis. Our analysis has uncovered four patterns of system design and points to unexplored regions of the design space, which may motivate future work in the field. Categories and Subject Descriptors Visual Interface Design, Tangible Interfaces Keywords Ubiquitous Computing, Ambient Display, Peripheral Display, Notification System, Taxonomy, Design Guidelines 1. INTRODUCTION From the very first formulation of Ubiquitous Computing, the idea of a calmer and more environmentally integrated way of displaying information has held intuitive appeal. Weiser called this ���calm computing��� [35] and described the area through an elegant example: a small, tangible representation of information in the world, a dangling string that would wiggle based on network traffic. When information can be conveyed via calm changes in the environment, users are more able to focus on their primary work tasks while staying aware of non-critical information that affects them. Research in this sub-domain goes by various names including ���ambient displays���, ���peripheral displays���, and ���notification systems���. The breadth of the systems in these broad categories is quite large. We seek to disentangle the terminology used to describe and categorize the wide array of systems in order to provide a common language for discussing research therein. An ambient display can represent many types of data, from stock prices, to weather forecasts, to the presence or absence of colleagues. Maintaining awareness of co-located and distant work and social groups has been a long-term research thread in the area of Computer Supported Cooperative Work (CSCW) [5, 8]. The Tangible Media Group at the MIT Media Lab, directed by Ishii, also helped shape the field of ambient computation. They coined the term ���tangible media,��� citing inspiration from Weiser���s vision [35] and from Pederson and Sokoler���s AROMA system [29] and developed AmbientROOM [17] and Ambient Fixtures [6, 18]. These systems use ambient displays to make people aware of both group activity and other information such as network traffic. Recent work in Ambient Intelligence has brought techniques from Artificial Intelligence to ambient systems, spearheaded by the Disappearing Computer initiative of the European Union [31]. This research thrust seeks to imbue ambient systems with contextual knowledge about the environment. The Roomware project has resulted in smart architectural spaces that support information conveyance (and group collaboration) [33]. Researchers have developed systems that use a multitude of everyday objects to display information. Examples include lights of various sorts [2, 17], sounds [25], shadows [8], artificial flowers [18], mobiles [24], and office-d��cor water fountains [12, 16]. Further research has sought to use framed photographs [26] and larger artistic pictures to represent information from the world in an art-like manner [14, 30, 32]. There are also peripheral display ���modes��� of a user���s main desktop, including screensavers like What���s Happening [36], information bars and menus such as those leveraged in Sideshow and Irwin [6, 22], and alternate panes, like Apple���s Dashboard [3]. As one can see, the design space is large. All these systems provide a rich history of system design principles, approaches, and decisions, but accumulating theoretical and craft knowledge has been stymied by the lack of a unified vocabulary to define and describe these systems. In this paper we propose a set of design choices that developers of ambient information systems must confront to build successful and compelling systems. First we set out a definition of an ambient information system that is a synthesis of the varied definitions given in published research. We hone the intuitive set of Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. AVI '06, May 23-26, 2006, Venezia, Italy. Copyright 2006 ACM 1-59593-353-0/06/0005. $5.00. 67

characteristics that distinguish ambient systems from other ubiquitous computing research systems. Next, we propose a set of design dimensions for ambient information systems. The four dimensions of system design elucidate the main decisions one confronts when designing an effective ambient system. Finally, we explore the clusters across dimensions to uncover four coherent combinations of system designs, which work as design patterns for the field. The results also identify new ways of combining the design attributes to explore new possibilities for ambient information systems. 2. AMBIENT INFORMATION SYSTEMS Many different terms have been used to describe the types of systems we discuss in this paper. Three of the most commonly used terms are ���ambient display,��� ���peripheral display,��� and ���notification system.��� But how does one differentiate these terms? Based on general understandings, we claim that: - all ambient displays are peripheral displays, - some notification systems are peripheral displays (some notification systems are not peripheral but are instead the object of focused work and attention) The words of researchers themselves likely best explain their conceptions of the systems that they have built. Below, we present germane definitional quotes. ��� Ishii et al: ���[In Ambient Displays] information is moved off the screen into the physical environment, manifesting itself as subtle changes in form, movement, sound, color, smell, temperature, or light. Ambient displays are well suited as a means to keep users aware of people or general states of large systems, like network traffic and weather.��� [17] ��� Matthews et al: Peripheral displays, then, are displays that show information that a person is aware of, but not focused on. [24] ��� Matthews et al: ���Ambient displays might be defined as those that are "minimally attended" (e.g. just salient enough for conscious perception) while alerting displays are "maximally divided" (e.g. slightly less salient than focal tasks). [24] ��� Stasko et al: Ambient displays typically communicate just one, or perhaps a few at the most, pieces of information and the aesthetics and visual appeal of the display is often paramount. Peripheral displays refer to systems that are out of a person���s primary focus of attention and may communicate one or more pieces of information.��� [32] ��� Mankoff et al: ���Ambient displays are abstract and aesthetic peripheral displays portraying non-critical information on the periphery of a user���s attention��� They generally support monitoring of non-critical information.��� ���Ambient displays have the ambitious goal of presenting information without distracting or burdening the user.��� [20] ��� Rounding and Greenberg: ���The [notification collage] is designed to present info[rmation] as lightweight and peripheral objects. It does not demand the full attention of its users: rather it can be attended to in passing, where people collaborate should the need or desire arise.��� [14] ��� McCrickard et al: ���Often implemented as ubiquitous systems or within a small portion of the traditional desktop, notification systems typically deliver information of interest in a parallel, multitasking approach, extraneous or supplemental to a user���s attention priority.��� [21] ��� McCrickard et al: Notification systems are defined as interfaces that are typically used in a divided-attention, multitasking situation, attempting to deliver current, valued information through a variety of platforms and modes in an efficient and effective manner [21]. The easiest way to explain the differences between systems is to look at the design motivations that informed them. Ambient displays are those that have pointed aesthetic goals and present a very small number of information elements. These systems are a proper subset of peripheral displays, which can appear either in the environment or on secondary or even primary computer displays. Notification systems��� design motivation results from divided attention situations. As such, they can be equal to a primary work task in their attentional needs or be secondary. When notification systems are designed to be secondary to a primary task, the systems are appropriately defined as peripheral. In this paper, we propose the term ambient information system as the unit of study and define the behavioral characteristics of such as systems as follows: ��� Display information that is important but not critical. ��� Can move from the periphery to the focus of attention and back again. ��� Focus on the tangible representations in the environment. ��� Provide subtle changes to reflect updates in information (should not be distracting). ��� Are aesthetically pleasing and environmentally appropriate. 3. PREVIOUS TAXONOMIES A small number of research papers that describe ambient information systems also include extended discussions of the design dimensions that motivate and contextualize their work. The authors provide dimensions to compare and contrast their systems to others in order to explain their design rationales. Matthews et al use the dimensions notification level, transition, and abstraction to characterize systems in this space [24]. They developed the Peripheral Display Toolkit [23] that helps people to develop ambient information displays more easily. Their concept of notification level means the relative importance of a particular data stream. Transitions are the programmatic changes to the display, based on the data. Transitions include fading, scrolling, or animation effects. They define abstraction as the mapping that takes a piece of numerical or ordinal data and turns it into something that the ambient display can use, something ���more easily interpreted with less [user] attention.��� Matthews et al segregate notification level into five levels: Ignore, Change Blind, Make Aware, Interrupt, and Demand Attention. The gradations run from low, a system ignoring the change in the data, to high, a system demanding attention in a way that must also be explicitly dismissed. They propose categories of transition: interrupt, make aware, and change blind. Finally, they bifurcate abstraction into feature abstraction or degradation. McCrickard et al introduce a different set of three dimensions to classify notification systems: interruption, reaction, and comprehension [21]. Interruption is defined psychologically, similar to Matthews��� notion, ���as an event prompting transition and reallocation of attention focus from a [primary] task to the notification.��� Reaction is defined as the rapid response to a given stimulus, while comprehension is the long-term notion of remembering and sense-making. 68