@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://aclanthology.org/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."
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<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.</abstract>
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%0 Conference Proceedings
%T Comonadic Morphophonology: A Compositional Framework for Context-Dependent Morphological Rules in Finnish
%A Jang, Yongseok
%Y Voigt, Rob
%Y Warstadt, Alex
%Y Feldman, Naomi
%Y Linzen, Tal
%S Proceedings of the Society for Computation in Linguistics 2026
%D 2026
%8 July
%I Association for Computational Linguistics
%C San Diego, CA
%@ 979-8-89176-412-5
%F jang-2026-comonadic
%X 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.
%U https://aclanthology.org/2026.scil-main.10/
%P 100-112
Markdown (Informal)
[Comonadic Morphophonology: A Compositional Framework for Context-Dependent Morphological Rules in Finnish](https://aclanthology.org/2026.scil-main.10/) (Jang, SCiL 2026)
ACL