Deterministic two-way transducers with pebbles (aka pebble transducers) capture the class of polyregular functions, which extend the string-to-string regular functions allowing polynomial growth instead of linear growth. One of the most fundamental operations on functions is composition, and (poly)regular functions can be realized as a composition of several simpler functions. In general, composition of deterministic two-way transducers incur a doubly exponential blow-up in the size of the inputs. A major improvement in this direction comes from the fundamental result of Dartois et al. [Luc Dartois et al., 2017] showing a polynomial construction for the composition of reversible two-way transducers. A precise complexity analysis for existing composition techniques of pebble transducers is missing. But they rely on the classic composition of two-way transducers and inherit the double exponential complexity. To overcome this problem, we introduce reversible pebble transducers. Our main results are efficient uniformization techniques for non-deterministic pebble transducers to reversible ones and efficient composition for reversible pebble transducers.
@InProceedings{dartois_et_al:LIPIcs.CONCUR.2025.14, author = {Dartois, Luc and Gastin, Paul and Germerie Guizouarn, Lo\"{i}c and Krishna, Shankaranarayanan}, title = {{Reversible Pebble Transducers}}, booktitle = {36th International Conference on Concurrency Theory (CONCUR 2025)}, pages = {14:1--14:22}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-389-8}, ISSN = {1868-8969}, year = {2025}, volume = {348}, editor = {Bouyer, Patricia and van de Pol, Jaco}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.14}, URN = {urn:nbn:de:0030-drops-239645}, doi = {10.4230/LIPIcs.CONCUR.2025.14}, annote = {Keywords: Transducers, Polyregular functions, Reversibility, Composition, Uniformization} }
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