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arXiv 1508.06976cs.DBcs.AI
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事件流上的实时的Top-K预测查询处理

Real-time Top-K Predictive Query Processing over Event Streams

University of Vermont(佛蒙特大学)

Saurav Acharya, Byung Suk Lee, Paul Hines

摘要:

本文解决了预测的k个事件,最有可能发生的下一个,在历史实时的【形】事件流的问题。因果预测查询的现有方法具有许多限制。首先,他们在非循环因果网络中进行彻底搜索,以找到最有可能的k效应事件;然而,来自真实事件流的数据经常反映循环因果关系。其次,它们包含保守的假设,旨在排除因果网络中所有可能的非因果联系;这导致遗漏了许多不太频繁但重要的因果联系。我们克服了这些限制,提出了一种新的事件优先模型和运行时的因果推理机制。事件优先模型在事件流上构造了一个一阶吸收马尔可夫链,其中两个事件之间的边表示它们之间的时间优先关系,这是因果关系的必要条件。然后,运行时因果推理机制在查询处理过程中动态学习因果关系。这是通过删除一些在事件优先级模型中存在其他事件时不显示因果关系的时间优先级关系来实现的。本文提出了两种查询处理算法--一种是对模型进行穷举搜索,另一种是对模型进行更有效的简化搜索并提前终止。利用两个真实数据集(电力系统中的连锁停电和网页浏览量)的实验验证了概率top-k预测查询的有效性和算法的效率。具体来说,减少搜索算法减少了运行时间,相对于穷举搜索,由25-80%(取决于应用程序),只有一个小的准确性降低。

英文摘要:

This paper addresses the problem of predicting the k events that are most likely to occur next, over historical real-time event streams. Existing approaches to causal prediction queries have a number of limitations. First, they exhaustively search over an acyclic causal network to find the most likely k effect events; however, data from real event streams frequently reflect cyclic causality. Second, they contain conservative assumptions intended to exclude all possible non-causal links in the causal network; it leads to the omission of many less-frequent but important causal links. We overcome these limitations by proposing a novel event precedence model and a run-time causal inference mechanism. The event precedence model constructs a first order absorbing Markov chain incrementally over event streams, where an edge between two events signifies a temporal precedence relationship between them, which is a necessary condition for causality. Then, the run-time causal inference mechanism learns causal relationships dynamically during query processing. This is done by removing some of the temporal precedence relationships that do not exhibit causality in the presence of other events in the event precedence model. This paper presents two query processing algorithms -- one performs exhaustive search on the model and the other performs a more efficient reduced search with early termination. Experiments using two real datasets (cascading blackouts in power systems and web page views) verify the effectiveness of the probabilistic top-k prediction queries and the efficiency of the algorithms. Specifically, the reduced search algorithm reduced runtime, relative to exhaustive search, by 25-80% (depending on the application) with only a small reduction in accuracy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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