Nelson R. Manohar

The session capture and replay paradigm for asynchronous collaboration

In this paper, we describe a paradigm and its associated collaboration artifact to allow flexible support for asynchronous collaboration. Under this paradigm, a user session with an applications user interface is encapsulated into a data artifact, referred to as a session object. Users collaborate by annotating, by modifying, and by a back-and-forth exchange of these session objects. Each session object is composed of several data streams that encapsulate audio annotations and user interactions with the application. The replay of a session object is accomplished by dispatching these data streams to the application for re-execution Re-execution of these streams is kept synchronized to maintain faithfulness to the original recording. The basic mechanisms allow a participant who misses a session with an application to catch up on the activities that occurred during the session. This paper presents the paradigm, its applications, its design, and our preliminary experience with its use.

Replay by Re-execution: A Paradigm for Asynchronous Collaboration via Record and Replay of Interactive Multimedia Sessions

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Dealing with synchronization and timing variability in the playback of interactive session recordings

In this paper, we describe scheduling and synchronization support for a novel multimedia document, referred to as a session object. The session object captures a voice-annotated, interactive session with an application | it contains audio and window streams. This paper addresses media scheduling and synchronization issues for the support of faithful replay of session objects when subject to timing variability at the replay workstation. The replay is supported by an adaptive scheduling algorithm. The algorithm preserves relative interstream synchronization between window and audio streams. Run-time temporal deformations are applied over the schedule of the window stream. We show that the inter-stream asynchrony oats under statistical control as a function of the scheduling interval. The mechanisms could be generalized to the replay of streams that are subject to timing variability. Our object-oriented toolkit, ReplayKit, enables an application to become replay-aware through access to session capture and replay functionality.

Applying statistical process control to the adaptive rate control problem

Due to the heterogeneity and shared resource nature of todays computer network environments, the end-to-end delivery of multimedia requires adaptive mechanisms to be effective. We present a framework for the adaptive streaming of heterogeneous media. We introduce the application of online statistical process control (SPC) to the problem of dynamic rate control. In SPC, the goal is to establish (and preserve) a state of statistical quality control (i.e., controlled variability around a target mean) over a process. We consider the end-to-end streaming of multimedia content over the internet as the process to be controlled. First, at each client, we measure process performance and apply statistical quality control (SQC) with respect to application-level requirements. Then, we guide an adaptive rate control (ARC) problem at the server based on the statistical significance of trends and departures on these measurements. We show this scheme facilitates handling of heterogeneous media. Last, because SPC is designed to monitor long-term process performance, we show that our online SPC scheme could be used to adapt to various degrees of long-term (network) variability (i.e., statistically significant process shifts as opposed to short-term random fluctuations). We develop several examples and analyze its statistical behavior and guarantees.

A flexible architecture for heterogeneous replayable workspaces

This paper presents a novel and flexible architecture to support the asynchronous sharing of computer-supported workspaces (CSWs), or simply replayable workspaces. Such workspaces are composed of multiple, interacting tools. Through the capture, re-execution, and manipulation of a session with a CSW, it is possible to reuse valuable collaborative information, (e.g., the how-to process). The session is encapsulated into a session object composed of heterogeneous media streams that represent input sequences to CSW tools. CSW tools are modeled as plug-in components to the CSW. A stream controller process extends temporal-awareness to a CSW tool and its media. A session manager coordinates the various stream controllers and their media. The architecture provides flexible coordination of the various tools found on a CSW and fine-grained integration of their heterogeneous media.