文章基本信息

标题：When Is a Bottom-Up Deterministic Tree Translation Top-Down Deterministic?
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作者：Sebastian Maneth ; Helmut Seidl
期刊名称：LIPIcs : Leibniz International Proceedings in Informatics
电子版ISSN：1868-8969
出版年度：2020
卷号：168
页码：134:1-134:18
DOI：10.4230/LIPIcs.ICALP.2020.134
出版社：Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik
摘要：We consider two natural subclasses of deterministic top-down tree-to-tree transducers, namely, linear and uniform-copying transducers. For both classes we show that it is decidable whether the translation of a transducer with look-ahead can be realized by a transducer without look-ahead. The transducers constructed in this way, may still make use of inspection, i.e., have an additional tree automaton restricting the domain. We provide a second procedure which decides whether inspection can be removed and if so, constructs an equivalent transducer without inspection. The construction relies on a fixpoint algorithm that determines inspection requirements and on dedicated earliest normal forms for linear as well as uniform-copying transducers which can be constructed in polynomial time. As a consequence, equivalence of these transducers can be decided in polynomial time. Applying these results to deterministic bottom-up transducers, we obtain that it is decidable whether or not their translations can be realized by deterministic uniform-copying top-down transducers without look-ahead (but with inspection) - or without both look-ahead and inspection.
关键词：Top-Down Tree Transducers; Earliest Transformation; Linear Transducers; Uniform-copying Transucers; Removal of Look-ahead; Removal of Inspection