2,959 research outputs found

    Optimization of Analytic Window Functions

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    Analytic functions represent the state-of-the-art way of performing complex data analysis within a single SQL statement. In particular, an important class of analytic functions that has been frequently used in commercial systems to support OLAP and decision support applications is the class of window functions. A window function returns for each input tuple a value derived from applying a function over a window of neighboring tuples. However, existing window function evaluation approaches are based on a naive sorting scheme. In this paper, we study the problem of optimizing the evaluation of window functions. We propose several efficient techniques, and identify optimization opportunities that allow us to optimize the evaluation of a set of window functions. We have integrated our scheme into PostgreSQL. Our comprehensive experimental study on the TPC-DS datasets as well as synthetic datasets and queries demonstrate significant speedup over existing approaches.Comment: VLDB201

    Learning to Navigate Cloth using Haptics

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    We present a controller that allows an arm-like manipulator to navigate deformable cloth garments in simulation through the use of haptic information. The main challenge of such a controller is to avoid getting tangled in, tearing or punching through the deforming cloth. Our controller aggregates force information from a number of haptic-sensing spheres all along the manipulator for guidance. Based on haptic forces, each individual sphere updates its target location, and the conflicts that arise between this set of desired positions is resolved by solving an inverse kinematic problem with constraints. Reinforcement learning is used to train the controller for a single haptic-sensing sphere, where a training run is terminated (and thus penalized) when large forces are detected due to contact between the sphere and a simplified model of the cloth. In simulation, we demonstrate successful navigation of a robotic arm through a variety of garments, including an isolated sleeve, a jacket, a shirt, and shorts. Our controller out-performs two baseline controllers: one without haptics and another that was trained based on large forces between the sphere and cloth, but without early termination.Comment: Supplementary video available at https://youtu.be/iHqwZPKVd4A. Related publications http://www.cc.gatech.edu/~karenliu/Robotic_dressing.htm

    Coordination in a Digital Platform Organization

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    A digital platform (DP) generates value by facilitating direct interactions between two or multiple platform sides. While previous studies have expounded upon how platform sides can be coordinated at a collective level (i.e., by pricing strategy and modular architecture), digital platform owners must not neglect the dynamics within the platform sides and their interactions. Through an in-depth case study of one of the largest e-commerce platforms worldwide, we develop a process model that explains digital platform coordination in terms of the mechanisms that describe the emergence of coordination issues as a result of the enactment of the platform sides’ agency and how these issues can be circumvented. This study makes two contributions. First, this study challenges the existing DP literature concerning the assumption of exogenous platform sides, highlighting the agency of the sides as a source of misalignment that must be managed. Second, the model complements the platform coordination literature focusing on enabling/constraining the actions of sides by conceptualizing a digital orienting mechanism. By adopting a meta-organizational view of digital platforms, this empirical work is among the few studies that report from the inside of a digital platform organization and adopt a processual account
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