QCMUQ@QALB-2015 Shared Task: Combining Character level MT and Error-tolerant Finite-State Recognition for Arabic Spelling Correction
Paper · 2015 · Houda Bouamor, Hassan Sajjad, Nadir Durrani et al.
Summary
This paper describes the joint CMU-Q and QCRI entry to the QALB-2015 shared task, which asks systems to fix errors in Modern Standard Arabic text. The test covers two genres: Aljazeera news comments (L1) and sentences written by non-native students of Arabic (L2). The errors vary widely, from split and merged words to letter-level slips and punctuation, so the authors built a cascade of specialised correctors. Each one takes the previous one's output.
The stages are:
- MADAMIRA's Alif/Ya fixes
- hand-written rules
- phrase-based and character-level SMT models built with Moses
- an error-tolerant finite-state recognizer that proposes dictionary words within a small edit distance, ranked by a language model
The best chain is Morph+CBMT+Rules+EFST. On the official 2015 test it scored F1 68.12 on L1 and 38.90 on L2, ranking 5th and 2nd respectively. The work shows that cheap, complementary correctors, each aimed at one error type, can add up to a strong system for a language with few resources.
Key points
- Training and evaluation use QALB corpus data and the m2Scorer. Language models come from GigaWord Arabic plus News Commentary (about 32M sentences, ~1.7B tokens), but only a random 60% was used because of compute limits.
- The dictionary is a 9-million-word Arabic list generated from the AraComLex transducer (Attia et al., 2012). It was compiled into an FST with Foma for error-tolerant lookup.
- The CBMT model treats each sentence as a sequence of characters. It uses MGIZA alignment, grow-diagonal-final symmetrization and 5-gram KenLM models.
- It was the strongest single module: F1 64.07 on the 2014 test and 39.07 on L2 dev.
- MADAMIRA corrections alone are very precise (P 78.33) but have low recall (31.27).
- Adding Morph in front of PBMT raised F1 by 3.22 points.
- The full chain reached F1 68.42 on the 2014 test (P 70.14, R 66.79) and 44.02 on L2 dev, against 20.28 for the Morph baseline.
- Official 2015 test scores: L1 P 71.39, R 65.13; L2 P 50.37, R 31.68.
Interesting ideas
- I1. Rather than one corrector for everything, the authors chain narrow experts, each aimed at one error class, and keep a combination only if the dev score rises. This makes every fix attributable to a specific module.
- I2. Spelling repair is framed as translation over characters, with spaces as ordinary symbols, so a single model learns both word splits and merges.
- I3. The error-tolerant finite-state recognizer finds dictionary words within a small edit distance (insertions, deletions, substitutions, transpositions), and a language model then picks among the candidates.
- I4. A data analysis revealed that one conjunction accounts for 95% of merge errors, which justified a targeted rule instead of a general model.
- I5. High-precision, low-recall modules are placed early, and higher-recall ones run on their output, which improves both precision and recall together.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (tokens): Mova's input normalisation could be a sequence of small, separately scored repair passes for spacing, casing, elongation and typos, each logging what it changed.
- I2 (tokens): a character-level noisy-to-clean model could repair glued or broken English tokens before tagging, rather than relying only on tokenizer heuristics.
- I3 (tokens): Mova's lexicon could be compiled into an FST so that out-of-vocabulary words get explainable nearest-word candidates before lemmatisation.
- I4 (learn): self-induced repair rules could be mined in the same way, by counting which few patterns dominate parser failures and promoting those to explicit rules.
- I5 (learn): when merging witness parsers for silver data, conservative high-precision rules could be applied first, leaving the remaining arcs to broader models.
Institutions
Fields, topics and concepts
📚 Shelves 6The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksArts and Humanities · 16,039 worksLanguage and Linguistics · 15,891 worksSocial Sciences · 1,772 worksEducation · 203 works
🧭 Topics 3Research subjects and languages the work is about.Machine translation · 1,087 worksSemitic languages · 2,908 worksGrammatical error correction & learner language · 156 works
Cite
Cite as Houda Bouamor, Hassan Sajjad, Nadir Durrani and Kemal Oflazer. 2015. QCMUQ@QALB-2015 Shared Task: Combining Character level MT and Error-tolerant Finite-State Recognition for Arabic Spelling Correction. Proceedings of the Second Workshop on Arabic Natural Language Processing.
@inproceedings{bouamor2015qcmuq,
title = {{QCMUQ@QALB-2015 Shared Task: Combining Character level MT and Error-tolerant Finite-State Recognition for Arabic Spelling Correction}},
author = {Houda Bouamor, Hassan Sajjad, Nadir Durrani and Kemal Oflazer},
booktitle = {Proceedings of the Second Workshop on Arabic Natural Language Processing},
year = {2015},
doi = {10.18653/v1/w15-3217},
url = {https://doi.org/10.18653/v1/w15-3217}
}References
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