A Query System for XML Data Stream and its Semanticsbased Buffer Reduction
A Query System for XML Data Stream and its Semanticsbased Buffer Reduction
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发表时间：
2010-05
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通讯作者：
Chi Yang;Chengfei Liu;Jianxin Li;J. Yu;Junhu Wang
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作者：
Chi Yang;Chengfei Liu;Jianxin Li;J. Yu;Junhu Wang
对于当前的XML数据流查询评估方法，采用某些类型的缓冲技术是不可避免的。在许多情况下，缓冲区规模可能会呈指数级增长，这可能会导致内存瓶颈。一些优化技术已被提出来解决这个问题。然而，这些技术的限制已被定义的并发下限，并已在理论上证明。在本文中，我们通过实证研究表明，这一下限可以打破考虑到缓冲区减少语义信息。为了证明这一点，我们建立了一个基于SAX的XML流查询评估系统，并设计了一个算法，消耗符合并发下限的缓冲区。在进一步分析下界的基础上，设计了几条突破下界的语义规则，并将这些规则融入到下界算法中。实验结果表明，单独和集体部署语义规则的算法都显着优于下界算法，不考虑语义信息。
With respect to current methods for query evaluation over XML data streams, adoption of certain types of buffering techniques is unavoidable. Under lots of circumstances, the buffer scale may increase exponentially, which can cause memory bottleneck. Some optimization techniques have been proposed to solve the problem. However, the limit of these techniques has been defined by a concurrency lower bound and has been theoretically proved. In this paper, we show through an empirical study that this lower bound can be broken by taking semantic information into account for buffer reduction. To demonstrate this, we built a SAX-based XML stream query evaluation system and designed an algorithm that consumes buffers in line with the concurrency lower bound. After a further analysis of the lower bound, we designed several semantic rules for the purpose of breaking the lower bound and incorporated these rules in the lower bound algorithm. Experiments are conducted to show that the algorithms deploying semantic rules individually and collectively all significantly outperform the lower bound algorithm that does not consider semantic information.