arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1004.2372cs.DBcs.FL
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从XML数据中学习确定性正则表达式进行模式推理

Learning Deterministic Regular Expressions for the Inference of Schemas from XML Data

Geert Jan Bex, Wouter Gelade, Frank Neven, Stijn Vansummeren

摘要:

为给定的XML文档集合推断适当的DTD或XML模式定义(XSD)实质上简化为从正例单词集合中学习确定性正则表达式。不幸的是,没有一个算法能够只从正例中学习确定性正则表达式的完整类,正如我们将要展示的那样。然而,在实际的DTD和XSD中出现的正则表达式使得每个字母符号只出现很少的次数。因此,在实践中,学习确定性正则表达式的子类就足够了,其中每个字母符号最多出现k次,对于某个小k。我们将这样的表达式称为k-出现正则表达式(简称k-ORE)。出于这种观察,我们提供了一个概率算法,学习k-ORE的增加值的k,并选择确定性的一个最好的描述样本的基础上的最小描述长度参数。该方法的有效性在真实世界和合成数据上都得到了经验验证。此外,该方法被证明是保守的,在以前的工作中考虑的表达式的简单类。

英文摘要:

Inferring an appropriate DTD or XML Schema Definition (XSD) for a given collection of XML documents essentially reduces to learning deterministic regular expressions from sets of positive example words. Unfortunately, there is no algorithm capable of learning the complete class of deterministic regular expressions from positive examples only, as we will show. The regular expressions occurring in practical DTDs and XSDs, however, are such that every alphabet symbol occurs only a small number of times. As such, in practice it suffices to learn the subclass of deterministic regular expressions in which each alphabet symbol occurs at most k times, for some small k. We refer to such expressions as k-occurrence regular expressions (k-OREs for short). Motivated by this observation, we provide a probabilistic algorithm that learns k-OREs for increasing values of k, and selects the deterministic one that best describes the sample based on a Minimum Description Length argument. The effectiveness of the method is empirically validated both on real world and synthetic data. Furthermore, the method is shown to be conservative over the simpler classes of expressions considered in previous work.

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