Computing devices and applications are now used beyond the desktop, in diverse environments, and this trend toward ubiquitous computing is accelerating. One challenge that remains in this emerging research field is the ability to enhance the behavior of any application by informing it of the context of its use. By context, we refer to any information that characterizes a situation related to the interaction between humans, applications and the surrounding environment. Context-aware applications promise richer and easier interaction, but the current state of research in this field is still far removed from that vision. This is due to three main problems: (1) the notion of context is still ill defined; (2) there is a lack of conceptual models and methods to help drive the design of context-aware applications; and (3) no tools are available to jump-start the development of context-aware applications. In this paper, we address these three problems in turn. We first define context, identify categories of contextual information, and characterize context-aware application behavior. Though the full impact of context-aware computing requires understanding very subtle and high-level notions of context, we are focusing our efforts on the pieces of context that can be inferred automatically from sensors in a physical environment. We then present a conceptual framework that separates the acquisition and representation of context from the delivery and reaction to context by a contextaware application. We have built a toolkit, the Context Toolkit, that instantiates this conceptual framework and supports the rapid development of a rich space of context-aware applications. We illustrate the usefulness of the conceptual framework by describing a number of contextaware applications that h...

. The proliferation ofcomputing into the physical world promises more than the ubiquitous availability of computing infrastructure; it suggests new paradigms of interaction inspired by constant access to information and computational capabilities. For the past decade, applicationdriven research in ubicomp has pushed three interaction themes: natural interfaces, context-aware applications, and automated capture and access. To chart a course for future research in ubiquitous computing, we review the accomplishments of these efforts and point to remaining research challenges. Research in ubiquitous computing implicitly requires addressing some notion of scale; whether in the number and type of devices, the physical space of distributed computing or the number of people using a system. We posit a new area of applications research, everyday computing, focussed on scaling interaction with respect to time. Just as pushing the availability of computing away from the traditional desktop fun...

The role of computers in the modern office has tended to split our activities between virtual interactions in the realm of the computer and physical interactions with real objects that have been part of the traditional office infrastructure. This paper discusses a variety of scenarios we have implemented in which the physical world can be invisibly and seamlessly augmented with electronic tags in order to connect physical objects with virtual representations or computational functionality. We demonstrate the utility of linking physical objects to electronic services and actions that are naturally associated with their form (e.g., a dictionary and a web-based translation service). Unlike previous work in this area, we have focused on uniquely combining four inexpensive technologies with off-the-shelf applications, everyday objects, and computational devices. KEYWORDS: RFID tag, ubiquitous computing, tangible interface, physical UI, phicon, augmented reality. INTRODUCTION Six years ag...

Context is a key issue in interaction between human and computer, describing the surrounding facts that add meaning. In mobile computing research published the parameter location is most often used to approximate context and to implement context-aware applications. We propose that ultra-mobile computing, characterized by devices that are operational and operated while on the move (e.g. PDAs, mobile phones, wearable computers), can significantly benefit from a wider notion of context. To structure the field we introduce a working model for context, discuss mechanisms to acquire context beyond location, and application of context-awareness in ultra-mobile computing. We investigate the utility of sensors for context-awareness and present two prototypical implementations - a light sensitive display and an orientation aware PDA interface. The concept is then extended to a model for sensor fusion to enable more sophisticated context recognition. Based on an implementation of the model an exp...

We describe sensing techniques motivated by unique aspects of human-computer interaction with handheld devices in mobile settings. Special features of mobile interaction include changing orientation and position, changing venues, the use of computing as auxiliary to ongoing, real-world activities like talking to a colleague, and the general intimacy of use for such devices. We introduce and integrate a set of sensors into a handheld device, and demonstrate several new functionalities engendered by the sensors, such as recording memos when the device is held like a cell phone, switching between portrait and landscape display modes by holding the device in the desired orientation, automatically powering up the device when the user picks it up the device to start using it, and scrolling the display using tilt. We present an informal experiment, initial usability testing results, and user reactions to these techniques.

Reading frequently involves not just looking at words on a page, but also underlining, highlighting and commenting, either on the text or in a separate notebook. This combination of reading with critical thinking and learning is called active reading [2]. To explore the premise that computation can enhance active reading we have built the XLibris "active reading machine." XLibris uses a commercial high-resolution pen tablet display along with a paper-like user interface to support the key affordances of paper for active reading: the reader can hold a scanned image of a page in his lap and mark on it with digital ink. To go beyond paper, XLibris monitors the free-form ink annotations made while reading, and uses these to organize and to search for information. Readers can review, sort and filter clippings of their annotated text in a "Reader's Notebook." XLibris also searches for material related to the annotated text, and displays links to similar documents unobtrusively in the margin. XLibris demonstrates that computers can help active readers organize and find information while retaining many of the advantages of reading on paper. Keywords Paper-like user interface, reading online, affordances of paper, pen computing, dynamic hypertext, document metaphor, information retrieval

We propose a navigation technique for browsing large documents that integrates rate-based scrolling with automatic zooming. The view automatically zooms out when the user scrolls rapidly so that the perceptual scrolling speed in screen space remains constant. As a result, the user can efficiently and smoothly navigate through a large document without becoming disoriented by extremely fast visual flow. By incorporating semantic zooming techniques the user can smoothly access a global overview of the document during rate-based scrolling. We implemented several prototype systems, including a web browser, map viewer, image browser, and dictionary viewer. An informal usability study suggests that for a document browsing task, most subjects prefer automatic zooming and the technique exhibits approximately equal performance time to scroll bars , suggesting that automatic zooming is a helpful alternative totraditional scrolling when the zoomed out view provides appropriate visual cues. KE...

This paper discusses the use of gesture and non-speech audio as ways to improve the user interface of a mobile music player. Their key advantages mean that users could use a player without having to look at its controls when on the move. Two very different evaluations of the player took place: one based on a standard usability experiment (comparing the new player to a standard design) and the other a video analysis of the player in use. Both of these showed significant usability improvements for the gesture/audiobased interface over a standard visual/pen-based display. The similarities and differences in the results produced by the two studies are discussed.

. In order for a smart environment to provide services to its occupants, it must be able to detect its current state or context and determine what actions to take based on the context. We discuss the requirements for dealing with context in a smart environment and present a software infrastructure solution we have designed and implemented to help application designers build intelligent services and applications more easily. We describe the benefits of our infrastructure through applications that we have built. 1 Introduction One of the goals of a smart environment is that it supports and enhances the abilities of its occupants in executing tasks. These tasks range from navigating through an unfamiliar space, to providing reminders for activities, to moving heavy objects for the elderly or disabled. In order to support the occupants, the smart environment must be able to both detect the current state or context in the environment and determine what actions to take based on this context...

The small size of handheld computers provides the convenience of mobility at the expense of reduced screen space for display and interaction. Prior research [5, 6] has identified the value of spatially aware displays, in which a position-tracked display provides a window on a larger virtual workspace. This paper builds on that work by suggesting two-handed interaction techniques combining pen input with spatially aware displays. Enabling simultaneous navigation and manipulation yields the ability to create and edit objects larger than the screen and to drag and drop in 3-D. Four prototypes of the Peephole Display hardware were built, and several Peephole-augmented applications were written, including a drawing program, map viewer, and calendar. Multiple applications can be embedded into a personal information space anchored to the user's physical reference frame. A usability study with 24 participants shows that the Peephole technique can be more effective than current methods for navigating information on handheld computers.