Aperiodic String Transducers

Luc Dartois (1) , Ismaël Jecker (1) , Pierre-Alain Reynier (2, 3)

1 ULB - Département d'Informatique [Bruxelles]
2 LIS - Laboratoire d'Informatique et des Systèmes (LIS) (Marseille, Toulon)
3 MOVE - Modélisation et Vérification

Regular string-to-string functions enjoy a nice triple characterization through deterministic two-way transducers (2DFT), streaming string transducers (SST) and MSO definable functions. This result has recently been lifted to FO definable functions, with equivalent representations by means of aperiodic 2DFT and aperiodic 1-bounded SST, extending a well-known result on regular languages. In this paper, we give three direct transformations: i) from 1-bounded SST to 2DFT, ii) from 2DFT to copyless SST, and iii) from k-bounded to 1-bounded SST. We give the complexity of each construction and also prove that they preserve the aperiodicity of transducers. As corollaries, we obtain that FO definable string-to-string functions are equivalent to SST whose transition monoid is finite and aperiodic, and to aperiodic copyless SST.

Domaines: Théorie et langage formel [cs.FL]

Luc Dartois, Ismaël Jecker, Pierre-Alain Reynier. Aperiodic String Transducers. International Journal of Foundations of Computer Science, 2018. ⟨hal-02003676⟩