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# Parser combinators for Tigrinya and Oromo morphology

**Authors:** Patrick Littell; Tom McCoy; [Na-Rae Han](https://md.mova.elamur.ai/free/en/docs/papers/authors/na-rae-han/); Shruti Rijhwani; Zaid Sheikh; David Mortensen; [Teruko Mitamura](https://md.mova.elamur.ai/free/en/docs/papers/authors/teruko-mitamura/); [Lori Levin](https://md.mova.elamur.ai/free/en/docs/papers/authors/lori-levin/) · **Year:** 2018 · **Venue:** Proceedings of the Eleventh International Conference on Language Resources and Evaluation (LREC 2018) **Link:** [aclanthology.org/L18-1611](https://aclanthology.org/L18-1611/) · library `lingbulk-2018-littell-parser-combinators-tigrinya-oromo-morphology` · **Licence:** [CC BY-NC 4.0](https://creativecommons.org/licenses/by-nc/4.0/) (ELRA, LREC proceedings) — summary only

[**1** citations in our library](https://md.mova.elamur.ai/free/en/docs/papers/cited-by/lingbulk-2018-littell-parser-combinators-tigrinya-oromo-morphology/) of the 140673 papers whose bibliographies we read[Proceedings of the Eleventh International Conference on Language Resources and Evaluation (LREC 2018)](https://aclanthology.org/volumes/L18-1/)[licence](https://creativecommons.org/licenses/by-nc/4.0/)

- [Publisher's page](https://aclanthology.org/L18-1611/)
- [PDF](https://aclanthology.org/L18-1611.pdf)

**Authors (8)**

1. Patrick Littell
2. Tom McCoy
3. Na-Rae Han
4. Shruti Rijhwani
5. Zaid Sheikh
6. David Mortensen
7. Teruko Mitamura
8. Lori Levin

Citations and author metrics from OpenAlex (); authors with the same name are not always told apart.

## What it is about

The authors write rule-based morphological parsers for Tigrinya and Oromo as parser combinators in Python, not as finite-state transducers. The work was done within a few days during the LoReHLT17 surprise-language evaluation. One grammar yields several outputs at once: breakdown, lemma, gloss and a natural English gloss, ranked by penalties. Tigrinya internal plurals are handled by regular-expression templates over consonant classes, and a Cost channel penalises over-analysis, for example place names that end in -a. The cost of finite-state efficiency is accepted. The evaluation is downstream: adding lemmatization raised entity detection and linking (typed_mention_ceaf_plus, Tigrinya 0.478 to 0.521, Oromo 0.355 to 0.376) and situation-frame F1 (Tigrinya 0.325 to 0.333, Oromo 0.047 to 0.086).

## Ideas

- I1. A cost channel for segmentation in `tools/hbo`: each prefix or suffix cut carries a penalty, so an unsplit word wins unless the stem is in the lexicon. This stops over-segmentation of names, the same way the paper stops `ʔuɡanɨda` from being read as a possessive `-a`. Where: the ranking of the `lex` and `pre` splits.
- I2. Templates as explicit patterns for Hebrew and Aramaic root-and-pattern plurals: a consonant-class pattern over the root triple, applied after the lexicon lookup, as the paper does for Tigrinya internal plurals. Where: [The Noun, the Adjective and the Numeral](https://md.mova.elamur.ai/free/en/docs/languages/hbo/04-noun/), [The noun in Biblical Aramaic](https://md.mova.elamur.ai/free/en/docs/languages/arc/nouns/), implemented as a fallback in `tools/hbo`.
- I3. Measure every added rule as the paper does, by its downstream effect (here, the lemma versus the word), with a before/after table. A rule is kept only if the downstream number rises on held-out data. Where: [13. Biblical Hebrew in Mova: the tools](https://md.mova.elamur.ai/free/en/docs/languages/hbo/13-mova-tools/).

## For Mova

I1 goes into `tools/hbo` (segmenter ranking). I2 goes into [The Noun, the Adjective and the Numeral](https://md.mova.elamur.ai/free/en/docs/languages/hbo/04-noun/) and [The noun in Biblical Aramaic](https://md.mova.elamur.ai/free/en/docs/languages/arc/nouns/), with its code in `tools/hbo`. I3 is the evaluation rule for [13. Biblical Hebrew in Mova: the tools](https://md.mova.elamur.ai/free/en/docs/languages/hbo/13-mova-tools/).

## Cite

The paper itself, not this card. BibTeX from the library's record of the work.

```
@inproceedings{littell2018parser,
  title = {{Parser combinators for Tigrinya and Oromo morphology}},
  author = {Littell, Patrick and McCoy, Tom and Han, Na-Rae and Rijhwani, Shruti and Sheikh, Zaid and Mortensen, David and Mitamura, Teruko and Levin, Lori},
  booktitle = {Proceedings of the Eleventh International Conference on Language Resources and Evaluation (LREC 2018)},
  year = {2018},
  url = {https://aclanthology.org/L18-1611/}
}
```

- [← previous Joint Prediction of Morphosyntactic Categories for Fine-Grained Arabic Part-of-Speech Tagging Exploiting Tag Dictionary Information](https://md.mova.elamur.ai/free/en/docs/papers/lingbulk-2017-inoue-joint-prediction-morphosyntactic-categories-fine/)
- [next → Build Fast and Accurate Lemmatization for Arabic](https://md.mova.elamur.ai/free/en/docs/papers/lingbulk-2018-mubarak-build-fast-accurate-lemmatization-arabic/)
- [↑ back to Semitic languages](https://md.mova.elamur.ai/free/en/docs/papers/sem/)

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