Rewrite rule grammars with multitape automata

Abstract

The majority of computational implementations of phonological and morphophonological alternations rely on composing together individual finite state transducers that represent sound changes.  Standard composition algorithms do not maintain the intermediate representations between the ultimate input and output forms.  These intermediate strings, however, can be very helpful for various tasks: enriching information (indispensable for models of historical linguistics), providing new avenues to debugging complex grammars, and offering explicit alignment information between morphemes, sound segments, and tags.  This paper describes a multi-tape automaton approach to creating full models of sequences of sound alternation that implement phonological and morphological grammars. A model and a practical implementation of multitape automata is provided together with a multitape composition algorithm tailored to the representation used in this paper.  Practical use cases of the approach are illustrated through two common examples; a phonological example of a complex rewrite rule grammar where multiple rules interact and a diachronic example of modeling sound change over time.