Untwisting two-way transducers in elementary time

• Published in: 2017 32nd Annual ACM/IEEE Symposium on Logic in Computer Science (LICS)
• Main Authors: Baschenis, Félix, Gauwin, Olivier, Muscholl, Anca, Puppis, Gabriele
• Other Authors: Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), ANR-13-JS02-0010,EXSTREAM,Extensions du traitement par flux(2013), ANR-16-CE40-0007,DELTA,DÉfis pour la Logique, les Transducteurs et les Automates(2016)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2017
• Subjects: two-way transducers; automata; [INFO.INFO-FL]Computer Science [cs]/Formal Languages and Automata Theory [cs.FL]; Iceland
• Online Access: https://hal.science/hal-01864614; https://hal.science/hal-01864614/document; https://hal.science/hal-01864614/file/final_lics17.pdf; https://doi.org/10.1109/LICS.2017.8005138

International audience Functional transductions realized by two-way transducers (equivalently, by streaming transducers and by MSO transductions) are the natural and standard notion of "regular" mappings from words to words. It was shown recently (LICS'13) that it is decidable if such a transduction can be implemented by some one-way transducer, but the given algorithm has non-elementary complexity. We provide an algorithm of different flavor solving the above question, that has double exponential space complexity. We further apply our technique to decide whether the transduction realized by a two-way transducer can be implemented by a sweeping transducer, with either known or unknown number of passes.