LegalSim-PT: Building a Dataset for Legal Document Simplification in Portuguese Leveraging Linguistic Metrics
Summary
Most document-level text simplification research targets English. Portuguese has had no sizable resource for simplifying whole documents, especially legal ones, whose dense syntax and specialized vocabulary hinder public access to justice. The authors address this gap with LegalSim-PT, a synthetic parallel corpus of complex and simplified Brazilian legal documents. They took source texts from the Brazilian portion of LegalPT and had the compact Qwen3-4B model produce simplified versions. They then kept only pairs that passed automatic checks for semantic consistency, readability gain and diversity, which reduces the need for manual review.
The corpus was assessed in several ways:
- surface statistics compared against existing simplification corpora;
- human ratings;
- two LLM judges;
- fine-tuning experiments with open models, evaluated with D-SARI, semantic similarity and Flesch.
Models fine-tuned on LegalSim-PT produced more readable outputs that kept more of the source meaning than their base versions. This makes the dataset a useful public benchmark and training resource for Portuguese legal simplification.
Key points
- Construction: The source is LegalPT (about 12M documents in 11 sub-datasets), of which the six Brazilian-law sub-datasets were used. Qwen3-4B generated the simplifications with an 8,192-token context and a 4,096-token output cap, and only about 2% of documents went over this limit. Filtering relied on chunk-level Sentence-BERT similarity, readability and diversity. The data is released on GitHub (scalercio/legal-doc-simplification-data).
- Human evaluation: 40 document pairs were rated.
- LLM judges: GPT-OSS-120B and LLaMA-70B both ranked the outputs Ours > Qwen2.5 > Bode. Weighted Cohen's κ between the judges was 0.74 overall and 0.85 on hard samples.
- Fine-tuning on the LegalSim-PT test set: Qwen2.5 rose from 35.74 to 50.78 in D-SARI, from 31.8 to 42.7 in Flesch, and from .653 to .810 in SIM. Qwen3 rose from 32.16 to 37.22 in D-SARI.
- Other baselines and cross-dataset results: Bode and Tucano served as Portuguese LLM baselines and struggled to preserve content in long documents. On the sentence-level GovLang-BR set, fine-tuning raised Flesch but lowered D-SARI, mostly because the models deleted less.
Cite
@inproceedings{scalercio2026legalsim,
title = {{LegalSim-PT: Building a Dataset for Legal Document Simplification in Portuguese Leveraging Linguistic Metrics}},
author = {Scalercio, Arthur and Finatto, Maria José and Paes, Aline},
booktitle = {Proceedings of the 17th International Conference on Computational Processing of Portuguese (PROPOR 2026) - Vol. 1},
year = {2026},
url = {https://aclanthology.org/2026.propor-1.39/}
}References
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