@inproceedings{jang-2026-comonadic,
    title = "Comonadic Morphophonology: A Compositional Framework for Context-Dependent Morphological Rules in {F}innish",
    author = "Jang, Yongseok",
    editor = "Voigt, Rob  and
      Warstadt, Alex  and
      Feldman, Naomi  and
      Linzen, Tal",
    booktitle = "Proceedings of the Society for Computation in Linguistics 2026",
    month = jul,
    year = "2026",
    address = "San Diego, CA",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingest-acl-workshops/2026.scil-main.10/",
    pages = "100--112",
    ISBN = "979-8-89176-412-5",
    abstract = "Composing finite-state transducers (FSTs) for context-dependent morphophonological rules{---}consonant gradation, vowel harmony, possessive suffix assimilation{---}leads to multiplicative state explosion; neural models sidestep the problem but provide no formal account of the rules themselves. We present the first framework where each morphophonological rule is a function from a focused local context to a single output segment{---}the type of a local rule familiar from cellular automata{---}and where length-changing rules compose as coKleisli arrows of a comonad. Our central contribution is the Writer comonad (DeletionSet x Zipper), a new algebraic construction that restores strict coKleisli compositionality for such rules: each rule is a coKleisli arrow, extend lifts it to a global transformation, and deletions accumulate as a monoid action rather than requiring intermediate materialization. As supporting evidence, thirteen coKleisli arrows provide an alternative formulation expressing the same morphophonological behaviors that Omorfi encodes via 874 continuation classes (67:1 reduction at the rule-representation level), and the same abstraction enables bidirectional morphology{---}a MorphGenerator reuses the analysis arrows for generation. On UD Finnish-TDT, the system achieves 83.92{\%} UPOS accuracy with rule-only disambiguation (94.66{\%} with an external suffix tagger), validating the framework as a practical morphological engine."
}