Streaming tree transducers with single-use restriction (${\mathrm{STT}}_{\mathrm{sur}}\mathrm{s}$) were introduced by Alur and D'Antoni as an analyzable, executable, and expressive model for transforming unranked ordered trees in a single pass. The equivalence problem of ${\mathrm{STT}}_{\mathrm{sur}}\mathrm{s}$ is decidable because their class is as expressive as the class of MSO-definable tree transformations. In this paper, we present streaming ranked-tree-to-string transducers (SRTSTs), based on ${\mathrm{STT}}_{\mathrm{sur}}\mathrm{s}$: SRTSTs are released from the single-use restriction while their input and output are restricted to ranked trees and strings, respectively. We show that the expressiveness of SRTSTs coincides with that of deterministic top-down tree transducers with regular look-ahead (${\mathrm{yDT}}^{\mathrm{R}}\mathrm{s}$), whose equivalence problem is known to be decidable. Our proof is done by constructing equivalent transducers in both directions.

具有一次性使用限制的流式树换能器（${\mathrm{STT}}_{\mathrm{苏尔}}\mathrm{s}$）是由Alur和D'Antoni引入的，它是一种可分析的，可执行的和表达性的模型，用于一次转换未排序的有序树。的等价问题${\mathrm{STT}}_{\mathrm{苏尔}}\mathrm{s}$之所以可以确定是因为它们的类与MSO可定义的树转换的类一样具有表现力。在本文中，我们基于以下内容介绍了流式排序树到字符串换能器（SRTST）：${\mathrm{STT}}_{\mathrm{苏尔}}\mathrm{s}$：SRTST从一次性使用限制中释放，而它们的输入和输出分别限于排序的树和字符串。我们显示，SRTST的表达与具有规则前瞻性的确定性自上而下的树换能器的表达相吻合（${\mathrm{yDT}}^{\mathrm{[R}}\mathrm{s}$），其等效问题已知是可以确定的。我们的证明是通过在两个方向上构造等效换能器来完成的。