Optimizing Tree Patterns for Querying Graph- and Tree-Structured Data

Wojciech Czerwinski, W. Martens, Matthias Niewerth, P. Parys
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引用次数: 7

Abstract

Many of today's graph query languages are based on graph pattern matching. We investigate optimization for treeshaped patterns with transitive closure. Such patterns are quite expressive, yet can be evaluated efficiently. The minimization problem aims at reducing the number of nodes in patterns and goes back to the early 2000's. We provide an example showing that, in contrast to earlier claims, tree patterns cannot be minimized by deleting nodes only. The example resolves the M ?/= NR problem, which asks if a tree pattern is minimal if and only if it is nonredundant. The example can be adapted to also understand the complexity of minimization, which was another question that was open since the early research on the problem. Interestingly, the latter result also shows that, unless standard complexity assumptions are false, more general approaches for minimizing tree patterns are also bound to fail in some cases.
优化树模式查询图和树结构数据
今天的许多图查询语言都是基于图模式匹配的。我们研究了具有传递闭包的树形模式的优化问题。这样的模式非常具有表现力,但是可以有效地进行评估。最小化问题旨在减少模式中的节点数量,这可以追溯到21世纪初。我们提供的示例表明,与前面的声明相反,树模式不能仅通过删除节点来最小化。该示例解决了M /= NR问题,该问题询问树模式是否最小,当且仅当它是非冗余的。这个例子也可以用来理解最小化的复杂性,这是对这个问题的早期研究以来的另一个开放的问题。有趣的是,后一个结果还表明,除非标准的复杂性假设是错误的,否则在某些情况下,用于最小化树模式的更一般的方法也必然会失败。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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