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arXiv 1402.0576cs.DBcs.AI
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基于OWL本体的SPARQL查询优化

Optimizing SPARQL Query Answering over OWL Ontologies

University of Ulm(乌尔姆大学);National Technical University of Athens(雅典国家技术大学)

Ilianna Kollia, Birte Glimm

摘要:

SPARQL查询语言目前正在由万维网联盟(W3C)用所谓的蕴涵机制进行扩展。蕴涵机制定义了如何在比SPARQL标准简单蕴涵更有表达力的语义下评估查询,SPARQL标准简单蕴涵基于子图匹配。查询是非常有表现力的,因为变量可以出现在复杂的概念中,也可以绑定到概念或角色名称。在本文中,我们描述了一个声音和完整的算法OWL直接语义蕴涵制度。我们进一步提出了一些新的优化,如确定一个良好的查询执行顺序,查询重写技术的战略,并显示如何专门的OWL推理任务和概念和角色层次结构,可以用来减少查询执行时间。为了确定一个良好的执行顺序,我们提出了一个基于成本的模型,其中的成本是基于信息的概念和角色的实例,从一个OWL推理建立的模型抽象提取。我们提出了两种排序策略:静态和动态的。对于动态的情况下,我们提高了性能,利用一个单独的聚类方法,允许计算成本函数的基础上,从一个集群的一个单独的样本。我们提供了一个原型实现,并评估所提出的优化的效率。我们的实验研究表明,静态排序通常优于动态的准确统计时,可用。然而,当统计数据不太准确时,这种情况会发生变化,例如,由于不确定性推理的决定。对于超越合取实例查询的查询,我们观察到由于所提出的优化,提高了三个数量级。

英文摘要:

The SPARQL query language is currently being extended by the World Wide Web Consortium (W3C) with so-called entailment regimes. An entailment regime defines how queries are evaluated under more expressive semantics than SPARQLs standard simple entailment, which is based on subgraph matching. The queries are very expressive since variables can occur within complex concepts and can also bind to concept or role names. In this paper, we describe a sound and complete algorithm for the OWL Direct Semantics entailment regime. We further propose several novel optimizations such as strategies for determining a good query execution order, query rewriting techniques, and show how specialized OWL reasoning tasks and the concept and role hierarchy can be used to reduce the query execution time. For determining a good execution order, we propose a cost-based model, where the costs are based on information about the instances of concepts and roles that are extracted from a model abstraction built by an OWL reasoner. We present two ordering strategies: a static and a dynamic one. For the dynamic case, we improve the performance by exploiting an individual clustering approach that allows for computing the cost functions based on one individual sample from a cluster. We provide a prototypical implementation and evaluate the efficiency of the proposed optimizations. Our experimental study shows that the static ordering usually outperforms the dynamic one when accurate statistics are available. This changes, however, when the statistics are less accurate, e.g., due to nondeterministic reasoning decisions. For queries that go beyond conjunctive instance queries we observe an improvement of up to three orders of magnitude due to the proposed optimizations.

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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