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arXiv 1104.2599cs.FLcs.DB
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流式树传感器

Streaming Tree Transducers

Rajeev Alur, Loris D'Antoni

摘要:

树转换器的理论为理解规约语言的表达性和分析问题的复杂性提供了基础,该规约语言用于转换诸如XML文档的分层结构数据。我们介绍了流树传感器作为一个可分析的,可执行的,和表达的模型,在一个单一的通过转换无序有序树。给定输入树的线性编码,转换器对输入进行单次从左到右的传递,并使用有限状态控制、可见下推堆栈和有限数量的变量来计算线性时间内的输出,这些变量存储可以使用字符串连接和树插入操作组合的输出块。我们证明了该模型的表达性与使用一元二阶逻辑(MSO)定义的转换相一致。现有的树传感器模型要么无法实现所有MSO可定义的转换,要么需要定期前瞻,从而禁止单次实现。我们展示了各种分析问题,如类型检查和检查功能等价是我们的模型可解决的。

英文摘要:

Theory of tree transducers provides a foundation for understanding expressiveness and complexity of analysis problems for specification languages for transforming hierarchically structured data such as XML documents. We introduce streaming tree transducers as an analyzable, executable, and expressive model for transforming unranked ordered trees in a single pass. Given a linear encoding of the input tree, the transducer makes a single left-to-right pass through the input, and computes the output in linear time using a finite-state control, a visibly pushdown stack, and a finite number of variables that store output chunks that can be combined using the operations of string-concatenation and tree-insertion. We prove that the expressiveness of the model coincides with transductions definable using monadic second-order logic (MSO). Existing models of tree transducers either cannot implement all MSO-definable transformations, or require regular look ahead that prohibits single-pass implementation. We show a variety of analysis problems such as type-checking and checking functional equivalence are solvable for our model.

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