The sharing of digital materials within online communities has increased significantly in recent years. Our work focuses on promoting community information sharing in public spaces using large screen, interactive, digital poster boards called the Plasma Posters. In this chapter we first describe our fieldwork-led, iterative design process, and elaborate a number of design guidelines that resulted. Following this, the design and development of the Plasma Posters themselves and the underlying network infrastructure is discussed. Finally, we present results from qualitative and quantitative evaluations over the course of a ten-month deployment of three Plasma Posters within our own organization, a software research community made up of technologists and designers. We conclude with observations regarding ergonomic, social and other factors that were raised during the design and deployment and offer reflections on factors in the success of this deployment.

We describe a novel interface for presenting interactive content on public digital bulletin boards. Inspired by paper fliers on physical bulletin boards, posted content is displayed using 3D virtual fliers attached to a virtual corkboard by virtual pushpins. Fliers appear in different orientations, creating an attractive, informal look, and have autonomous behaviors like fluttering in the wind. Passers-by can rotate, move and fold fliers; they can also interact with fliers' live content. Flier content is streamed from a server and represented by the system on large screen displays using a real-time cloth simulation algorithm. We describe our prototype, and offer the results of an initial evaluative user study.

We present similarity-based methods to cluster digital photos by time and image content. The approach is general, unsupervised, and makes minimal assumptions regarding the structure or statistics of the photo collection. We present results for the algorithm based solely on temporal similarity, and jointly on temporal and content-based similarity. We also describe a supervised algorithm based on learning vector quantization. Finally, we include experimental results for the proposed algorithms and several competing approaches on two test collections.

We present a system that allows remote and local participants to control devices in a meeting environment using mouse or pen based gestures "through" video windows. Unlike state-of-the-art device control interfaces that require interaction with text commands, buttons, or other artificial symbols, our approach allows users to interact with devices through live video of the environment. This naturally extends our video supported pan/tilt/zoom (PTZ) camera control system, by allowing gestures in video windows to control not only PTZ cameras, but also other devices visible in video images. For example, an authorized meeting participant can show a presentation on a screen by dragging the file on a personal laptop and dropping it on the video image of the presentation screen. This paper presents the system architecture, implementation tradeoffs, and various meeting control scenarios.

To simplify the process of editing interactive video, we developed the concept of "detail-on-demand" video as a subset of general hypervideo. Detail-on-demand video keeps the authoring and viewing interfaces relatively simple while supporting a wide range of interactive video applications. Our editor, Hyper-Hitchcock, provides a direct manipulation environment in which authors can combine video clips and place hyperlinks between them. To summarize a video, Hyper-Hitchcock can also automatically generate a hypervideo composed of multiple video summary levels and navigational links between these summaries and the original video. Viewers may interactively select the amount of detail they see, access more detailed summaries, and navigate to the source video through the summary.

In this paper, we describe how a detail-on-demand representation for interactive video is used in video summarization. Our approach automatically generates a hypervideo composed of multiple video summary levels and navigational links between these summaries and the original video. Viewers may interactively select the amount of detail they see, access more detailed summaries, and navigate to the source video through the summary. We created a representation for interactive video that supports a wide range of interactive video applications and Hyper-Hitchcock, an editor and player for this type of interactive video. Hyper-Hitchcock employs methods to determine (1) the number and length of levels in the hypervideo summary, (2) the video clips for each level in the hypervideo, (3) the grouping of clips into composites, and (4) the links between elements in the summary. These decisions are based on an inferred quality of video segments and temporal relations those segments.

The FXPAL Photo Application is designed to faciliate the organization of digital images from digital cameras and other sources through automated organization and intuitive user interfaces.

We demonstrate the use of detail-on-demand hypervideo in interactive training and video summarization. Detail-on-demand video allows viewers to watch short video segments and to follow hyperlinks to see additional detail. The player for detail-ondemand video displays keyframes indicating what links are available at each point in the video. The Hyper-Hitchcock authoring tool helps users create hypervideo by automatically dividing video into clips that can be combined in a direct manipulation interface. Clips can be grouped into composites and hyperlinks can be placed between clips and composites. A summarization algorithm creates multi-level hypervideo summaries from linear video by automatically selecting clips and placing links between them.

We present a framework for summarizing digital media based on structural analysis. Though these methods are applicable to general media, we concentrate here on characterizing repetitive structure in popular music. In the first step, a similarity matrix is calculated from inter-frame spectral similarity. Segment boundaries, such as verse-chorus transitions, are found by correlating a kernel along the diagonal of the matrix. Once segmented, spectral statistics of each segment are computed. In the second step, segments are clustered based on the pairwise similarity of their statistics, using a matrix decomposition approach. Finally, the audio is summarized by combining segments representing the clusters most frequently repeated throughout the piece. We present results on a small corpus showing more than 90% correct detection of verse and chorus segments.

This demonstration introduces UbiComp attendees to a system for content annotation and open-air, social blogging on interactive, publicly situated, digital poster boards using public and personal devices. We describe our motivation, a scenario of use, our prototype, and an outline of the demonstration.

As the Internet and related technologies for communication change, the role of communication in the conduct of business changes with it. Communication used to be viewed as a technical problem of separating signal from noise and managing bandwidth. Now it is a social matter in which negotiating differences in understanding among 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 that help deal with potential breakdowns in social interaction.

We present similarity-based methods to cluster digital photos by time and image content. This approach is general, unsupervised, and makes minimal assumptions regarding the structure or statistics of the photo collection. We describe versions of the algorithm using temporal similarity with and without content-based similarity, and compare the algorithms with existing techniques, measured against ground-truth clusters created by humans.

This paper presents a video acquisition system that can learn automatic video capture from human's camera operations. Unlike a predefined camera control system, this system can easily adapt to its environment changes with users' help. By collecting users' camera-control operations under various environments, the control system can learn video capture from human, and use these learned skills to operate its cameras when remote viewers don't, won't, or can't operate the system. Moreover, this system allows remote viewers to control their own virtual cameras instead of watching the same video produced by a human operator or a fully automatic system. The online learning algorithm and the camera management algorithm are demonstrated using field data.

Motivation: EST data reflects variation in gene expression, but previous methods for finding coexpressed genes in EST data are subject to bias and vastly overstate the statistical significance of putatively coexpressed genes. Results: We introduce a new method (LNP) that reports reasonable $p$-values and also detects more biological relationships in human dbEST than do previous methods. In simulations with human dbEST library sizes, previous methods report $p$-values as low as $10^{-30}$ on 1/1,000 uncorrelated pairs, while LNP reports significance correctly. We validate the analysis on real human genes by comparing coexpressed pairs to GO annotations and find that LNP is more sensitive than three previous methods. We also find a small but statistically significant level of coexpression between interacting proteins relative to randomized controls. The LNP method is based on a log-normal prior on the distribution of expression levels. Availability: Source code in Java or R is available at http://ests.sourceforge.net/

Hypervideo is a form of interactive video that allows users to follow links to other video. A simple form of hypervideo, called "detail-on-demand video," provides at most one link from one segment of video to another, supporting a singlebutton interaction. Detail-on-demand video is well suited for interactive video summaries, because the user can request a more detailed summary while watching the video. Users interact with the video is through a special hypervideo player that displays keyframes with labels indicating when a link is available. While detail-on-demand summaries can be manually authored, it is a time-consuming task. To address this issue, we developed an algorithm to automatically generate multi-level hypervideo summaries. The highest level of the summary consists of the most important clip from each take or scene in the video. At each subsequent level, more clips from each take or scene are added in order of their importance. We give one example in which a hypervideo summary is created for a linear training video. We also show how the algorithm can be modified to produce a hypervideo summary for home video.

Community poster boards serve an important community building function. Posted fliers advertise services, events and people's interests, and invite community members to communicate, participate, interact and transact. In this paper we describe the design, development and deployment of the Plasma Poster Network, a network of large screen, digital community poster boards, the Plasma Posters. An initial deployment of Plasma Posters is within our own organization, a software research community made up of technologists and designers. We present our motivation and two fieldwork studies of online and offline information sharing before describing the Plasma Posters and the underlying information storage and distribution infrastructure. Finally, we summarize findings from qualitative and quantitative evaluations of Plasma Poster usage and conclude by elaborating on socio-technical challenges that have been faced in the design and deployment of the Plasma Poster Network.

Much effort has been expended in creating online information resources to foster social networks, create synergies between collocated and remote colleagues, and enhance social capital within organizations. Following the observation that physical bulletin boards serve an important community building and maintenance function, in this paper we describe a network of large screen, digital bulletin boards, the Plasma Poster Network. The function of this system is to bridge the gap between online community interactions and shared physical spaces. We describe our motivation, a fieldwork study of information sharing practices within our organization, and an internal deployment of Plasma Posters.

Much effort has been expended in creating online spaces for people to meet, network, share and organize. However, there is relatively little work, in comparison, that has addressed creating awareness of online community activities for those gathered together physically. We describe our efforts to advertise the online community spaces of CHIplace and CSCWplace using large screen, interactive bulletin boards that show online community information mixed with content generated at the conference itself. Our intention was to raise awareness of the online virtual community within the offline, face-to-face event. We describe the two deployments, at CHI 2002 and at CSCW 2002, and provide utilization data regarding people's participation within the physical and virtual locales.

To simplify the process of editing interactive video, we developed the concept of "detail-on-demand" video as a subset of general hypervideo where a single button press reveals additional information about the current video sequence. Detail-on-demand video keeps the authoring and viewing interfaces relatively simple while supporting a wide range of interactive video applications. Our editor, Hyper-Hitchcock, builds on prior work on automatic analysis to find the best quality video clips. It introduces video composites as an abstraction for grouping and manipulating sets of video clips. Navigational links can be created between any two video clips or composites. Such links offer a variety of return behaviors for when the linked video is completed that can be tailored to different materials. Initial impressions from a pilot study indicate that Hyper-Hitchcock is easy to learn although the behavior of links is not immediately intuitive for all users.

With digital still cameras, users can easily collect thousands of photos. Our goal is to make organizing and browsing photos simple and quick, while retaining scalability to large collections. To that end, we created a photo management application concentrating on areas that improve the overall experience without neglecting the mundane components of such an application. Our application automatically divides photos into meaningful events such as birthdays or trips. Several user interaction mechanisms enhance the user experience when organizing photos. Our application combines a light table for showing thumbnails of the entire photo collection with a tree view that supports navigating, sorting, and filtering photos by categories such as dates, events, people, and locations. A calendar view visualizes photos over time and allows for the quick assignment of dates to scanned photos. We fine-tuned our application by using it with large personal photo collections provided by several users.

In a meeting room environment with multiple public wall displays and personal notebook computers, it is possible to design a highly interactive experience for manipulating and annotating slides. For the public displays, we present the ModSlideShow system with a discrete modular model for linking the displays into groups, along with a gestural interface for manipulating the flow of slides within a display group. For the applications on personal devices, an augmented reality widget with panoramic video supports interaction among the various displays. This widget is integrated into our NoteLook 3.0 application for annotating, capturing and beaming slides on pen-based notebook computers.

Existing hypertext systems have emphasized either the navigational or spatial expression of relationships between objects. We are exploring the combination of these modes of expression in Hyper-Hitchcock, a hypervideo editor. Hyper-Hitchcock supports a form of hypervideo called "detail-on-demand video" due to its applicability to situations where viewers need to take a link to view more details on the content currently being presented. Authors of detail-on-demand video select, group, and spatially arrange video clips into linear sequences in a two-dimensional workspace. Hyper-Hitchcock uses a simple spatial parser to determine the temporal order of selected video clips. Authors add navigational links between the elements in those sequences. This combination of navigational and spatial hypertext modes of expression separates the clip sequence from the navigational structure of the hypervideo. Such a combination can be useful in cases where multiple forms of inter-object relationships must be expressed on the same content.

Many readers annotate passages that are important to their work. If we understand the relationship between the types of marks on a passage and the passage's ultimate utility in a task, then we can design e-book software to facilitate access to the most important annotated parts of the documents. To investigate this hypothesis and to guide software design, we have analyzed annotations collected during an earlier study of law students reading printed case law and writing Moot Court briefs. This study has allowed us to characterize the relationship between the students' annotations and the citations they use in their final written briefs. We think of annotations that relate directly to the written brief as high-value annotations; these annotations have particular, detectable characteristics. Based on this study we have designed a mark parser that analyzes freeform digital ink to identify such high-value annotations.

In this article we argue that discourse structure constrains the set of possible constituents in a discourse that can provide the relevant context for structuring information in a target sentence, while information structure critically constrains discourse structure ambiguity. For the speaker, the discourse structure provides a set of possible contexts for continuation while information structure assignment is independent of discourse structure. For the hearer, the information structure of a sentence together with discourse structure instructs dynamic semantics how rhematic information should be used to update the meaning representation of the discourse (Polanyi and van den Berg, 1996).