Chat programs and instant messaging services are increasingly popular among Internet users. However, basic issues with the interfaces and data structures of most forms of chat limit their utility for use in formal interactions (like group meetings) and decision-making tasks. In this paper, we discuss Threaded Text Chat, a program designed to address some of the deficiencies of current chat programs. Standard forms of chat introduce ambiguity into interaction in a number of ways, most profoundly by rupturing connections between turns and replies. Threaded Chat presents a solution to this problem by supporting the basic turn-taking structure of human conversation. While the solution introduces interface design challenges of its own, usability studies show that users' patterns of interaction in Threaded Chat are equally effective, but different (and possibly more efficient) than standard chat programs.

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Increasingly, documents exist primarily in digital form. System designers have recently focused on making it easier to read digital documents, with annotation as an important new feature. But supporting annotation well is difficult because digital documents are frequently modified, making it challenging to correctly reposition annotations in modified versions. Few systems have addressed this issue, and even fewer have approached the problem from the users' point of view. This paper reports the results of two studies examining user expectations for "robust" annotation positioning in modified documents. We explore how users react to lost annotations, the relationship between types of document modifications and user expectations, and whether users pay attention to text surrounding their annotations. Our results could contribute substantially to effective digital document annotation systems.

One vision of future technology is the ability to easily and inexpensively capture any group meeting that occurs, store it, and make it available for people to view anytime and anywhere on the network. One barrier to achieving this vision has been the design of low-cost camera systems that can capture important aspects of the meeting without needing a human camera operator. A promising solution that has emerged recently is omni-directional cameras that can capture a 360-degree video of the entire meeting.The panoramic capability provided by these cameras raises both new opportunities and new issues for the interfaces provided for post-meeting viewers -for example, do we show all meeting participants all the time or do we just show the person who is speaking, how much control do we provide to the end-user in selecting the view, and will providing this control distract them from their task. These are not just user interface issues, they also raise tradeoffs for the client-server systems used to deliver such content. They impact how much data needs to be stored on the disk, what computation can be done on the server vs. the client, and how much bandwidth is needed. We report on a prototype system built using an omnidirectional camera and results from user studies of interface preferences expressed by viewers.