Abowd, Gregory D.

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    Securing Context-Aware Applications Using Environment Roles
    (Georgia Institute of Technology, 2000) Covington, Michael J. ; Long, Wende ; Srinivasan, Srividhya ; Dey, Anind K. ; Ahamad, Mustaque ; Abowd, Gregory D.
    In the future, a largely invisible and ubiquitous computing infrastructure will assist people with a variety of activities in the home and at work. The applications that will be deployed in such systems will create and manipulate private information and will provide access to a variety of other resources. Securing such applications is challenging for a number of reasons. Unlike traditional systems where access control has been explored, access decisions may depend on the context in which requests are made. We show how the well-developed notion of roles can be used to capture security-relevant context of the environment in which access requests are made. By introducing environment roles, we create a uniform access control framework that can be used to secure context-aware applications. We also present a security architecture that supports security policies that make use of environment roles to control access to resources.
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    A Scalable Workload Model of Media-Enhanced Classrooms
    (Georgia Institute of Technology, 1999) Chervenak, Ann L. ; Vellanki, Vivekanand ; Yanasak, Ivan ; Harel, Nissim ; Rodenstein, Roy ; Abowd, Gregory D. ; Brotherton, Jason Alan ; Ramachandran, Umakishore
    We present a scalable workload model for media-enhanced classrooms. Such classrooms include equipment for presenting multimedia streams and for capturing streams of information (audio, video and notes) during a lecture. Our model characterizes the workload of a centralized or distributed server that supports multiple classrooms. The workload includes server bandwidth, network bandwidth and server storage requirements. Using our workload model, we present detailed performance measurements of one media-enhanced classroom system, Classroom 2000. We identify patterns in user behavior, and demonstrate that the number of simultaneous study sessions varies with time of day according to a beta distribution. In addition, we model the total number of study sessions on a particular day using a simple linear model that depends on proximity to midterm and final examinations. Finally, we use the model to predict how the capabilities of a Classroom 2000 server must scale to support hundreds of classrooms and thousands of students.
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    Scenario-Based Analysis of Software Architecture
    (Georgia Institute of Technology, 1995) Kazman, Rick ; Abowd, Gregory D. ; Bass, Leonard J. ; Clements, Paul
    Software architecture is one of the most important tools for designing and understanding a system, whether that system is in preliminary design, active deployment, or maintenance. Scenarios are important tools for exercising an architecture in order to gain information about a system's fitness with respect to a set of desired quality attributes. This paper presents a set of experiential case studies illustrating the methodological use of scenarios to gain architecture-level understanding and predictive insight into large, real-world systems in various domains. A structured method for scenario-based architectural analysis is presented, using scenarios to analyze architectures with respect to achieving quality attributes. Finally, lessons and morals are presented, drawn from the growing body of experience in applying scenario-based architectural analysis techniques.