Synthetic Data for English Lexical Normalization: How Close Can We Get to Manually Annotated Data?
What it is about
Lexical normalisation maps non-standard tweet words to standard ones, and supervised normalisers need annotated data that exists for few languages and domains. The authors generate training pairs from raw tweets in two directions: adding noise to clean tweets, and normalising noisy tweets without labels. Noise is added by Brown clusters, by two word-embedding neighbourhoods, and by a custom error generator with ten categories (typographical, missing apostrophe, spelling list, repetition, vowel shortening, slang, phonetic, and others). The MoNoise normaliser trained on the best generated data reaches 94.29% accuracy on the LexNorm1.2 test set, against 95.22% with human annotation and 88.45% for copying the input; the best fully unsupervised variant reaches 92.04%. In a human test, five annotators labelled 100 tweets as human or machine-written, with an average accuracy of 64.8%. In an ablation, removing the missing-apostrophe or phonetic category lowers accuracy most, while removing typographical errors has almost no effect.
Ideas
- I1.
en/src/morph.rsand 19. The lexicon: vocabulary, multiword expressions and register: write the noise categories as explicit rules (dropped apostrophe: "didn't" to "didnt"; "-ing" to "-in"; vowel removal), each generated pair carrying the rule that made it. A held-out gold set of learner or informal pairs then says which rules help. - I2. Keep the paper's conservative candidate vote: a normalisation is applied only when at least two independent sources agree, and a tie keeps the original word. Measure precision and recall on the held-out set; precision is the first number to report.
- I3. Ablation per rule, as the paper does (leave one category out, re-train, re-measure). Drop rules with no measurable effect, so the table stays small and explainable.
- I4. Use the paper's human-judgment design as a check of Mova's generated text: a blind sample of generated and real sentences with a written reason per judgment, scored against chance.
For Mova
The chapters are 06. Spelling rules: inflection, derivation, compounds and national standards for the noise rules, 07. Punctuation, capital letters, abbreviations and numbers for the apostrophe, and 19. The lexicon: vocabulary, multiword expressions and register for slang and register. The code points are en/src/morph.rs (rule tables), en/src/tok.rs (tokens and contractions) and en/src/dict.rs. The measure: normalisation accuracy, precision and recall on a held-out set, the per-rule ablation, all run twice for determinism, with a shuffled-pair negative control that must score lower.
Cite
@inproceedings{dekker2020synthetic,
title = {{Synthetic Data for English Lexical Normalization: How Close Can We Get to Manually Annotated Data?}},
author = {Dekker, Kelly and Goot, Rob van der},
booktitle = {Proceedings of the Twelfth Language Resources and Evaluation Conference},
year = {2020},
url = {https://aclanthology.org/2020.lrec-1.773/}
}References
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