Freeform digital ink annotation allows readers to interact with documents in an intuitive and familiar manner. Such marks are easy to manage on static documents, and provide a familiar annotation experience. In this paper, we describe an implementation of a freeform annotation system that accommodates dynamic document layout. The algorithm preserves the correct position of annotations when documents are viewed with different fonts or font sizes, with different aspect ratios, or on different devices. We explore a range of heuristics and algorithms required to handle common types of annotation, and conclude with a discussion of possible extensions to handle special kinds of annotations and changes to documents.

This work presents constructs called interactive space-time maps along with an application called the SpaceTime Browser for visualizing and retrieving documents. A 3D visualization with 2D planar maps and a time line is employed. Users can select regions on the maps and choose precise time intervals by sliding the maps along the telescopic time line. Regions are highlighted to indicate the presence of documents with matching space-time attributes, and documents are retrieved and displayed in an adjoining workspace. We provide two examples: (1) organizing travel photos, (2) managing documents created by room location-aware devices in a building.

This paper describes how the changing information about an individual's location, environment, and social situation can be used to initiate and facilitate people's interactions with one another, individually and in groups. Context-aware communication is contrasted with other forms of context-aware computing and we characterize applications in terms of design decisions along two dimensions: the extent of autonomy in context sensing and the extent of autonomy in communication action. A number of context-aware communication applications from the research literature are presented in five application categories. Finally, a number of issues related to the design of context-aware communication applications are presented.

Squeezing desktop Web content into smart phones and text pagers is more practical with separate interfaces for navigation and content manipulation. m-Links, a middleware proxy system, supports this dual-mode browsing, offering phonetop users an extendable set of actions.

We present methods for automatically producing summary excerpts or thumbnails of music. To find the most representative excerpt, we maximize the average segment similarity to the entire work. After window-based audio parameterization, a quantitative similarity measure is calculated between every pair of windows, and the results are embedded in a 2-D similarity matrix. Summing the similarity matrix over the support of a segment results in a measure of how similar that segment is to the whole. This measure is maximized to find the segment that best represents the entire work. We discuss variations on the method, and present experimental results for orchestral music, popular songs, and jazz. These results demonstrate that the method finds significantly representative excerpts, using very few assumptions about the source audio.

We present a method for characterizing both the rhythm and tempo of music. We also present ways to quantitatively measure the rhythmic similarity between two or more works of music. This allows rhythmically similar works to be retrieved from a large collection. A related application is to sequence music by rhythmic similarity, thus providing an automatic "disc jockey" function for musical libraries. Besides specific analysis and retrieval methods, we present small-scale experiments that demonstrate ranking and retrieving musical audio by rhythmic similarity.

As ubiquitous computing becomes widespread, we are increasingly coming into contact with "shared" computer-enhanced devices, such as cars, televisions, and photocopiers. Our interest is in identifying general issues in personalizing such shared everyday devices. Our approach is to compare alternative personalization methods by deploying and using alternative personalization interfaces (portable and embedded) for three shared devices in our workplace (a presentation PC, a plasma display for brainstorming, and a multi-function copier). This paper presents the comparative prototyping methodology we employed, the experimental system we deployed, observations and feedback from use, and resulting issues in designing personalized shared ubiquitous devices.

Evaluating ubiquitous systems is hard, and has attracted the attention of others in the research community. These investigators, like others in CSCW, argue there is a basic mismatch between traditional evaluation techniques and the needs posed by ubiquitous systems. Namely, these systems are embedded in a variety of complex real world environments that cannot be easily modeled (as required by theoretical analyses), simulated, measured, or controlled (as required by laboratory experiments). As a result, many investigators have abandoned traditional comparative evaluation techniques and opted instead for techniques adapted from the social sciences, such as anthropology. We wanted to perform a comparative evaluation similar to a laboratory experiment, but in such a way that we could observe the effects of our design decisions in relatively unconstrained, real world use. This led us to the process described in this paper.

The TactGuide is a mobile navigation device 'displaying' personalized direction cues by means of a tactile and 'tactful' representation. The TactGuide is operated by tactile inspection which is subtle enough to allow the users to engage/disengage in device interaction while preserving their visual, auditory and kinesthetic senses for inspection of the environment. The TactGuide design thereby accommodates the users' need to economize their attentional resources between device and environment while navigating through physical space. Preliminary experiments indicates that users readily map the tactile cues to spatial directions and that TactGuide can be operated as a supplement to, and without compromising, the use of our existing wayfinding abilities. substituting the use of our natural abilities and earned skills for wayfinding.

To implement any quantum operation (a.k.a. ``superoperator'' or ``CP map'') on a d-dimensional quantum system, it is enough to apply a suitable overall unitary transformation to the system and a d^2-dimensional environment which is initialized in a fixed pure state. It has been suggested that a d-dimensional environment might be enough if we could initialize the environment in a mixed state of our choosing. In this note we show with elementary means that certain explicit quantum operations cannot be realized in this way. Our counterexamples map some pure states to pure states, giving strong and easily manageable conditions on the overall unitary transformation. Everything works in the more general setting of quantum operations from d-dimensional to d'-dimensional spaces, so we place our counterexamples within this more general framework.

This volume is the edited proceedings of the ACM conference on Collabroative Virtual Environments.

We present a method for rapidly and robustly extracting audio excerpts without the overhead of speech recognition or speaker segmentation. An immediate application is to automatically augment keyframe-based video summaries with informative audio excerpts associated with the video segments represented by the keyframes. Short audio clips combined with keyframes comprise an extremely lightweight and Web-browsable interface for auditioning video or similar media, without using bandwidth-intensive streaming video or audio.

This paper presents a camera system called FlySPEC. In contrast to a traditional camera system that provides the same video stream to every user, FlySPEC can simultaneously serve different video-viewing requests. This flexibility allows users to conveniently participate in a seminar or meeting at their own pace. Meanwhile, the FlySPEC system provides a seamless blend of manual control and automation. With this control mix, users can easily make tradeoffs between video capture effort and video quality. The FlySPEC camera is constructed by installing a set of Pan/Tilt/Zoom (PTZ) cameras near a high-resolution panoramic camera. While the panoramic camera provides the basic functionality of serving different viewing requests, the PTZ camera is managed by our algorithm to improve the overall video quality that may affect users watching details. The video resolution improvements from using different camera management strategies are compared in the experimental section.

Given panoramic video taken along a self-intersecting path, we present a method for detecting the intersection points. This allows "virtual tours" to be synthesized by splicing the panoramic video at the intersection points. Spatial intersections are detected by finding the best-matching panoramic images from a number of nearby candidates. Each panoramic image is segmented into horizontal strips. Each strip is averaged in the vertical direction. The Fourier coefficients of the resulting 1-D data capture the rotation-invariant horizontal texture of each panoramic image. The distance between two panoramic images is calculated as the sum of the distances between their strip texture pairs at the same row positions. The intersection is chosen as the two candidate panoramic images that have the minimum distance.

We present a framework, motivated by rate-distortion theory and the human visual system, for optimally representing the real world given limited video resolution. To provide users with high fidelity views, we built a hybrid video camera system that combines a fixed wide-field panoramic camera with a controllable pan/tilt/zoom (PTZ) camera. In our framework, a video frame is viewed as a limited-frequency representation of some "true" image function. Our system combines outputs from both cameras to construct the highest fidelity views possible, and controls the PTZ camera to maximize information gain available from higher spatial frequencies. In operation, each remote viewer is presented with a small panoramic view of the entire scene, and a larger close-up view of a selected region. Users may select a region by marking the panoramic view. The system operates the PTZ camera to best satisfy requests from multiple users. When no regions are selected, the system automatically operates the PTZ camera to minimize predicted video distortion. High-resolution images are cached and sent if a previously recorded region has not changed and the PTZ camera is pointed elsewhere. We present experiments demonstrating that the panoramic image can effectively predict where to gain the most information, and also that the system provides better images to multiple users than conventional camera systems.

As the technology for communication changes, the role of communication in the conduct of business changes with it. Communication is no longer just a technical matter of separating signal from noise and managing bandwidth but also a social matter in which negotiating differences in understanding among and between communicators is a primary business priority. Addressing this priority requires an understanding of how individuals interact in the course of their decision making activities. Using the work of Anthony Giddens as a point of departure, this paper views interaction in communication as consisting of three dimensions - meaning, authority, and trust. These three dimensions are used to identify new opportunities for advances in decision making technology which help deal with potential breakdowns in social interaction.

A basic objective of Weiser's Ubiquitous Computing vision is ubiquitous information access: being able to utilize any content or service (e.g., all the rich media content and services on the WWW), using devices that are always "at hand" (embedded in environments or portable), over a network with universal coverage and adequate bandwidth. Although much progress has been made, the ideal remains elusive. This paper examines the inter-relations among three dimensions of ubiquitous information systems: (1) ubiquitous content; (2) ubiquitous devices; and (3) ubiquitous networking. We use the space defined by these dimensions to reflect on the tradeoffs designers make and to chart some past and current information systems. Given this background, we present m-Links (mobile links), a new system that takes aim at the elusive ideal of ubiquitous information. Our approach builds on wireless web phone technologies because of their trend towards ubiquitous devices and networking (the second and third dimensions). Yet such very small devices sacrifice usability as rich media Internet terminals (the first dimension). To offset this limitation, we propose a new information access model for very small devices that supports a much wider range of content and services than previously possible. We have built this system with an emphasis on open systems extensibility and describe its design and implementation.

Hypertext interfaces typically involve navigation, the act (and interaction) of moving from one piece of information to another. Navigation can be exploratory, or it may involve backtracking to some previously-visited node. While backtracking interfaces are common, they may not reflect differences in readers' purposes and mental models. This paper draws on some empirical evidence regarding navigation between and within documents to suggest improvements on traditional hypertext navigation, and proposes a time-based view of backtracking.

In the emerging world of electronic publishing how we create, distribute, and read books will be in a large part determined by an underlying framework of content standards that establishes the range of technological opportunities and constraints for publishing and reading systems. But efforts to develop content standards based on sound engineering models must skillfully negotiate competing and sometimes apparently irreconcilable objectives if they are to produce results relevant to the rapidly changing course of technology. The Open eBook Forum's Publication Structure, an XML-based specification for electronic books, is an example of the sort of timely and innovative problem solving required for successful real-world standards development. As a result of this effort, the electronic book industry will not only happen sooner and on a larger scale than it would have otherwise, but the electronic books it produces will be more functional, more interoperable, and more accessible to all readers. Public interest participants have a critical role in this process.

S. Vassilvitskii, J. Kubica, E. G. Rieffel, J. W. Suh, M. Yim

Shared text input is a technique we implemented into a note taking system for facilitating text entry on small devices. Instead of writing out words on the tedious text entry interfaces found on handheld computers, users can quickly reuse words and phrases already entered by others. Sharing notes during a meeting also increases awareness among note takers. We found that filtering the text to share was appropriate to deal with a variety of design issues such as screen real estate, scalability, privacy, reciprocity, and predictability of text location

In this paper, we describe an evaluation of the Palette, a presentation tool that was reported at CHI '99. The Palette allows presenters to quickly access digital presentations using physical cards that have unique barcodes printed on them. The Palette has been in use in our lab for over three years, and has been released as a product in Japan. Our evaluation consists of an analysis of usage logs, an expert walkthrough review, and observations and interviews with users, non-users and the system administrator. The findings reveal benefits and drawbacks of the technology, and offers design ideas for further work on tangible tools of this kind.

We describe our experiences with the design, implementation, deployment, and evaluation of a Portholes tool which provides group and collaboration awareness through the Web. The research objective was to explore how such a system would improve communication and facilitate a shared understanding among distributed development groups. During the deployment of our Portholes system, we conducted a naturalistic study by soliciting user feedback and evolving the system in response. Many of the initial reactions of potential users indicated that our system projected the wrong image so that we designed a new version that provided explicit cues about being in public and who is looking back to suggest a social rather than information interface. We implemented the new design as a Java applet and evaluated design choices with a preference study. Our experiences with different Portholes versions and user reactions to them provide insights for designing awareness tools beyond Portholes systems. Our approach is for the studies to guide and to provide feedback for the design and technical development of our system.

In this paper, we document an extension to traditional pattern-theoretic object templates to jointly accommodate variations in object pose and in the radiant appearance of the object surface. We first review classical object templates accommodating pose variation. We then develop an efficient subspace representation for the object radiance indexed on the surface of the three dimensional object template. We integrate the low-dimensional representation for the object radiance, or signature, into the pattern-theoretic template, and present the results of orientation estimation experiments. The experiments demonstrate both estimation performance fluctuations under varying illumination conditions and performance degradations associated with unknown scene illumination. We also present a Bayesian approach for estimation accommodating illumination variability.

The increasing number of wireless, portable devices has led inevitably to lyrical rhetorics of business cost-cutting and increased efficiency as workers can be productive while on the and offices become streamlined areas of efficient activity. In this short paper, we raise a number if issues that have been appearing in common discourses the (most) modern office, and the impact of wireless technologies thereupon. We also present an overview of a workshop held at ECSCW in Bonn in September of 2001 on this topic, giving an overview of the comments and discussions that took place at the workshop.

Recent years have seen a marked increase in the production and promotion of portable, wireless communication devices: mobile phones with internet access, wireless PDAs such as the Palm VII and smart pagers such as RIM's 850 and 950. Some claim the presence of such devices in the hands, bags and pockets of so many people heralds a new world of work in which people can be reached and information accessed "anywhere, anytime". Whether or not access to information in itself can promote new working practices, individuals whose lives revolve around movement between work sites have been singled out as an obvious market for such portable wireless communication devices. Using these devices such “mobile workers” can be in touch with colleagues, collaborators and clients "24/7", and still sustain non-work social relationships due, apparently, to their constant connectedness whilst mobile. In this chapter we have two goals. The first is to address the design of mobile technologies. This second is to illustrate our design approach, wherein we consider local practices of technology use, but also the broader cultural context in which technologies are designed, produced, bought, sold, used and redesigned. Our ultimate design aim is to build upon existing practices, but also to consider possibilities for the development of innovative technologies that enable new, complementary, practices.

In this paper, we present a novel framework for analyzing video using self-similarity. Video scenes are located by analyzing inter-frame similarity matrices. The approach is flexible to the choice of similarity measure and is robust and data-independent because the data is used to model itself. We present the approach and its application to scene boundary detection. This is shown to dramatically outperform a conventional scene-boundary detector that uses a histogram-based measure of frame difference.

Given rapid improvements in storage devices, network infrastructure and streaming-media technologies, a large number of corporations and universities are recording lectures and making them available online for anytime, anywhere access. However, producing high-quality lecture videos is still labor intensive and expensive. Fortunately, recent technology advances are making it feasible to build automated camera management systems to capture lectures. In this paper we report our design of such a system, including system configuration, audio-visual tracking techniques, software architecture, and user study. Motivated by different roles in a professional video production team, we have developed a multi-cinematographer single-director camera management system. The system performs lecturer tracking, audience tracking, and video editing all fully automatically, and offers quality close to that of human-operated systems.

We describe a system called FlyAbout which uses spatially indexed panoramic video for virtual reality applications. Panoramic video is captured by moving a 360° camera along continuous paths. Users can interactively replay the video with the ability to view any interesting object or choose a particular direction. Spatially indexed video gives the ability to travel along paths or roads with a map-like interface. At junctions, or intersection points, users can chose which path to follow as well as which direction to look, allowing interaction not available with conventional video. Combining the spatial index with a spatial database of maps or objects allows users to navigate to specific locations or interactively inspect particular objects.

This paper presents a novel approach to visualizing the time structure of musical waveforms. The acoustic similarity between any two instants of an audio recording is displayed in a static 2D representation, which makes structural and rhythmic characteristics visible. Unlike practically all prior work, this method characterizes self-similarity rather than specific audio attributes such as pitch or spectral features. Examples are presented for classical and popular music.

To meet the diverse needs of business, education, and personal video users, the authors developed three visual interfaces that help identify potentially useful or relevant video segments. In such interfaces, keyframes-still images automatically extracted from video footage-can distinguish videos, summarize them, and provide access points. Well-chosen keyframes enhance a listing's visual appeal and help users select videos. Keyframe selection can vary depending on the application's requirements: A visual summary of a video-captured meeting may require only a few highlight keyframes, a video editing system might need a keyframe for every clip, while a browsing interface requires an even distribution of keyframes over the video's full length. The authors conducted user studies for each of their three interfaces, gathering input for subsequent interface improvements. The studies revealed that finding a similarity measure for collecting video clips into groups that more closely match human perception poses a challenge. Another challenge is to further improve the video-segmentation algorithm used for selecting keyframes. A new version will provide users with more information and control without sacrificing the interface's ease of use.

A novel method for region of interest tracking and recording video is presented. The proposed method is based on the FlyCam system, which produces high resolution and wide-angle video sequences by stitching the video frames from multiple stationary cameras. The method integrates tracking and recording processes, and targets applications such as classroom lectures and video conferencing. First, the region of interest (which typically covers the speaker) is tracked using a Kalman filter. Then, the Kalman filter estimation results are used for virtual camera control and to record the video. The system has no physical camera motion and the virtual camera parameters are readily available for video indexing. The proposed system has been implemented for real time recording of lectures and presentations.

We introduce the beat spectrum, a new method of automatically characterizing the rhythm and tempo of music and audio. The beat spectrum is a measure of acoustic self-similarity as a function of time lag. Highly structured or repetitive music will have strong beat spectrum peaks at the repetition times. This reveals both tempo and the relative strength of particular beats, and therefore can distinguish between different kinds of rhythms at the same tempo. We also introduce the beat spectrogram which graphically illustrates rhythm variation over time. Unlike previous approaches to tempo analysis, the beat spectrum does not depend on particular attributes such as energy or frequency, and thus will work for any music or audio in any genre. We present tempo estimation results for a variety of musical genres, which are accurate to within 1%. This approach has a variety of applications, including music retrieval by similarity and automatically generating music videos.

This paper reports our design, and implementation of an automatic lecture-room camera-management system. The motivation for building this system is to facilitate online lecture access and reduce the expense of producing high quality lecture videos. The goal of this project is a camera-management system that can perform as a human video-production team. To achieve this goal, our system collects audio/video signals available in the lecture room and uses the multimodal information to direct our video cameras to interesting events. Compared to previous work--which has tended to be technology centric--we started with interviews with professional video producers and used their knowledge and expertise to create video production rules. We then targeted technology components that allowed us to implement a substantial portion of these rules, including the design of a virtual video director, a speaker cinematographer, and an audience cinematographer. The complete system is installed in parallel with a human-operated video production system in a middle-sized corporate lecture room, and used for broadcasting lectures through the web. The systemí*s performance was compared to that of a human operator via a user study. Results suggest that our system's quality is close to that of a human-controlled system.

The results from a series of three experiments that used Text Retrieval Conference (TREC) data and TREC search topics are compared. These experiments each involved three novel user interfaces (one per experiment). User interfaces that made it easier for users to view text were found to improve recall in all three experiments. A distinction was found between a cluster of subjects (a majority of whom were search experts) who tended to read fewer documents more carefully (readers, or exclusives) and subjects who skimmed through more documents without reading them as carefully (skimmers, or inclusives). Skimmers were found to have significantly better recall overall. A major outcome from our experiments at TREC and with the TREC data, is that hypertext interfaces to information retrieval (IR) tasks tend to increase recall. Our interpretation of this pattern of results across the three experiments is that increased interaction with the text (more pages viewed) generally improves recall. Findings from one of the experiments indicated that viewing a greater diversity of text on a single screen (i.e., not just more text per se, but more articles available at once) may also improve recall. In an experiment where a traditional (type-in) query interface was contrasted with a condition where queries were marked up on the text, the improvement in recall due to viewing more text was more pronounced with search novices. Our results demonstrate that markup and hypertext interfaces to text retrieval systems can benefit recall and can also benefit novices. The challenge now will be to find modified versions of hypertext interfaces that can improve precision, as well as recall and that can work with users who prefer to use different types of search strategy or have different types of training and experience.

R. Want and B. N. Schilit

In this paper we describe the Mobile Link (m-Links) infrastructure for utilizing existing World Wide Web content and services on wireless phones and other very small Internet terminals. Very small devices, typically with 3-20 lines of text, provide portability and other functionality while sacrificing usability as Internet terminals. In order to provide access on such limited hardware we propose a small device web navigation model that is more appropriate than the desktop computers web browsing model. We introduce a middleware proxy, the Navigation Engine, to facilitate the navigation model by concisely displaying the Webs link (i.e., URL) structure. Because not all Web information is appropriately "linked," the Navigation Engine incorporates data-detectors to extract bits of useful information such as phone numbers and addresses. In order to maximize program-data composibility, multiple network-based services (similar to browser plug-ins) are keyed to a links attributes such as its MIME type. We have built this system with an emphasis on user extensibility and we describe the design and implementation as well as a basic set of middleware services that we have found to be particularly important.

The goal of this project is to teach a computer-robot system to understand human speech through natural human-computer interaction. To achieve this goal, we develop an interactive and incremental learning algorithm based on entropy-guided learning vector quantisation (LVQ) and memory association. Supported by this algorithm, the robot has the potential to learn unlimited sounds progressively. Experimental results of a multilingual short-speech learning task are given after the presentation of the learning system. Further investigation of this learning system will include human-computer interactions that involve more modalities, and applications that use the proposed idea to train home appliances.

The two most commonly used techniques for evaluating the fit between application design and use - namely, usability testing and beta testing with user feedback - suffer from a number of limitations that restrict evaluation scale (in the case of usability tests) and data quality (in the case of beta tests). They also fail to provide developers with an adequate basis for: (1) assessing the impact of suspected problems on users at large, and (2) deciding where to focus development and evaluation resources to maximize the benefit for users at large. This paper describes an agent-based approach for collecting usage data and user feedback over the Internet that addresses these limitations to provide developers with a complementary source of usage- and usability-related information. Contributions include: a theory to motivate and guide data collection, an architecture capable of supporting very large scale data collection, and real-word experience suggesting the proposed approach is complementary to existing practice.

Hitchcock is a system to simplify the process of editing video. Its key features are the use of automatic analysis to find the best quality video clips, an algorithm to cluster those clips into meaningful piles, and an intuitive user interface for combining the desired clips into a final video. We conducted a user study to determine how the automatic clip creation and pile navigation support users in the editing process. The study showed that users liked the ease-of-use afforded by automation, but occasionally had problems navigating and overriding the automated editing decisions. These findings demonstrate the need for a proper balance between automation and user control. Thus, we built a new version of Hitchcock that retains the automatic editing features, but provides additional controls for navigation and for allowing users to modify the system decisions.