Proceedings

Proceedings of the NODALIDA 2011 Workshop Constraint Grammar Applications. Editors: Eckhard Bick, Kristin Hagen, Kaili Müürisep, Trond Trosterud. NEALT Proceedings Series, Vol. 14 (2011), vi+69 pp. © 2011 The editors and contributors. Published by Northern European Association for Language Technology (NEALT) http://omilia.uio.no/nealt . Electronically published at Tartu University Library (Estonia) http://hdl.handle.net/10062/19231

On Weakly Ambiguous Finite Transducers

Abstract. By weakly ambiguous (finite) transducers we mean those transducers that, although being ambiguous, may be viewed to be at arm’s length from unambiguity. We define input-unambiguous (IU) and input-deterministic (ID) transducers, and transducers with finite codomain (FC). IU transductions are characterized by nondeterministic bimachines and ID transductions can be represented as a composition of sequential functions and finite substitutions. FC transductions are recognizable and can be expressed as finite unions of subsequential func-tions. We place these families along with uniformly ambiguous (UA) and finitely ambiguous (FA) transductions in a hierarchy of ambiguity. Fi-nally, we show that restricted nondeterministic bimachines characterize FA transductions. Perhaps the most important aspect of this work con-sists in defining nondeterministic bimachines and describing their power by linking them with weakly ambiguous finite transducers (IU and FA).