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docs(WO77/E2): paper draft — the dispatch doctrine for underdetermined mappings (#334)
Draft 1 of the resources/evaluation paper: the two structural rules (vocalization-as-composition, abugida lexicon-first), the dispatch table, the negative-results registry as a first-class contribution (RL, CTC, LLM teachers, correlated distillation), the per-language results under external protocols, and VRR as the ambiguity-aware evaluation proposal. Owner review before any external submission. Co-authored-by: Ronald Tse <[email protected]>
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# Learning the Underdetermined: A Dispatch Doctrine for Neural Completion of Rule-Definable Script Mappings
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**Draft 1 — WO77/E2 (resources & evaluation paper). Owner review before any submission.**
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## Abstract
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Authority romanization systems are rules; the languages they romanize
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are not always rule-complete. Abjads omit vowels, abugidas imply them,
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and the residual ambiguity must be resolved by a model — a component
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that authorities do not govern and that the field has no shared
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methodology for building. This paper contributes a dispatch doctrine:
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an empirically derived mapping from (script class, ambiguity type,
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data regime) to training technique, grounded in a negative-results
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registry from a systematic campaign, two structural rules that govern
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the composition of learned components with rule systems, and an
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ambiguity-aware evaluation metric (valid-reading rate) that corrects
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the systematic undercounting of single-reference diacritization
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error rates. We report per-language results under external-protocol
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evaluation for Arabic, Urdu, Persian, Thai, Khmer, and Hebrew, and we
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release every verdict — positive and negative — in a machine-checkable
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registry.
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## 1. The underdetermination spectrum
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Script conversion mappings form a spectrum. At one pole, the mapping
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is a function the authority fully decrees: Cyrillic → Latin with a
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published correspondence table. At the other, the source orthography
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genuinely underdetermines the target: an Arabic skeleton (كتب) is a
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*relation* over readings (kataba, kutiba, kutub, ...), a Thai
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orthographic syllable underdetermines its tone, a Khmer cluster
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underdetermines its vowel. The intermediate zone — where the authority
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decrees conventions *conditioned on an inferred layer* — is where
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learned components belong.
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The design error this paper argues against is treating the whole
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spectrum as one problem class: applying one neural recipe to every
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language, or conversely, hand-rolling a new pipeline per language. The
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dispatch doctrine makes the technique choice a function of measurable
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properties of the language pair.
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## 2. The doctrine
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**Rule 1 — Vocalization is composition, not a sibling task.** An
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unvocalized skeleton is a relation over readings; vocalization upgrades
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it to a function, which the rule system then applies. The two must not
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be conflated: romanizing a bare skeleton by convention (what
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bibliographic systems do) is a different product from predicting the
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hidden reading. Composition, not pipeline ad-hocery: the rule language
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declares the call, the model fills the relation, the decode policy
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selects among licensed readings.
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**Rule 2 — Abugidas presuppose a reading.** Thai and Khmer
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orthographies are positional syllabaries: vowel signs interleave with
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consonant clusters, inherent vowels are implied, tone is computed from
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orthographic class — and the major romanization convention (RTGS)
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discards the tone that the orthography computes. The rule system is
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deterministic *over an inferred layer*. The doctrine: lexicon-first
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(dictionary hit-rate is the first-class metric), trained fallback for
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novel tokens, and a rule composite for the convention; the three
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target layers (toneless romanization, phonemic, phonemic + tone) are
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tracked separately.
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**The dispatch table** (script class × ambiguity × data regime →
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technique), with the registry-defaulted form: lexical ambiguity
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dominant → lexicon + morphology-conditioned SFT; phonotactic
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reordering → byte-level seq2seq (ByT5-class); register variance →
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register-stratified data; teacher availability → oracle relabel only
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when teacher arms disagree; distillation only across decorrelated
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teachers.
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## 3. The negative-results registry
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Four refuted techniques are recorded with the same rigor as positives,
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each with its motivating failure:
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- **Reinforcement learning for diacritization** is knowledge-limited at
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SFT convergence: the reward signal cannot exceed what the supervised
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model already knows.
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- **CTC** cannot model Thai phonotactics: the conditional independence
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of CTC paths escapes the mode collapse of seq2seq training but
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plateaus far above the byte-level seq2seq baseline.
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- **LLMs as label teachers** hallucinate diacritics at rates
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incompatible with training; banned by registry law, enforced by the
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pipeline validators.
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- **Distillation on correlated teacher arms** transfers nothing: arms
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trained on the same data family agree on the same errors, leaving no
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oracle signal. Complementarity, not accuracy, predicts transfer.
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## 4. Per-language programs
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| language | task | technique (dispatch) | result | external protocol |
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|---|---|---|---|---|
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| Arabic | diacritization | ByT5 SFT + oracle relabel + noisy-student chain | DER 2.29 (canonical), 4.57 (fast tier) | SadeedDiac-25 |
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| Arabic | news register | register-closure specialist | WER 8.85 | WikiNews-2024 multiref |
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| Urdu | diacritization | base-model SFT | CER 3.57 | held-out docs split |
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| Persian | diacritization | SFT + register work | CER 0.603 row-mean | 9,288-row docs split |
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| Thai | G2P | lexicon-first + ByT5 fallback (CTC refuted) | PER 2.85 | published G2P suite |
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| Khmer | transliteration | lexicon-conditioned ByT5 (in progress) | CER 27.4 → target < 15 | held-out corpus |
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| Hebrew | nikud | plane architecture (data-gated) | DER 8.18 int8 | ReNikud protocol |
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## 5. Evaluation: valid-reading rate
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Single-reference DER counts every divergence from one gold reading as
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an error, systematically undercounting models that produce *other
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licensed readings*. We propose reporting valid-reading rate (VRR) —
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the proportion of predictions that are dictionary-licensed readings —
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alongside DER/WER, and evaluating multireference sets with
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oracle-validity rather than best-match. The multireference
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reconciliation failures that motivated this are documented with
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examples.
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## 6. Governance
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Every claim in Section 4 links to a frozen artifact: a pinned corpus
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(SHA-256, license-reviewed), a conformance-vector set reproduced
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byte-exactly in three independent runtimes, a prediction file, and an
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external protocol. Verdicts live in a machine-checkable registry that
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the training pipeline consults; refuted techniques require a new
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register entry to retry.
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## 7. Conclusion
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The dispatch doctrine converts per-language modeling from craft to
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policy: measurable properties select the technique, the registry
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prevents re-treading refuted ground, and the evaluation admits
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legitimate ambiguity. The doctrine is released as registry defaults so
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that the next language is a configuration, not a research project.
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## References (to complete)
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- ByT5; sequitur G2P; SadeedDiac-25; ReNikud; PyThaiNLP.
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- The negative-results registry (interscript-models TODO.sota).
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- RTGS; UNGEGN romanization; the ISC formalism (companion paper).

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