Span NLI BERT for ContractNLI

ContractNLI is a dataset for document-level natural language inference (NLI) on contracts whose goal is to automate/support a time-consuming procedure of contract review. In this task, a system is given a set of hypotheses (such as "Some obligations of Agreement may survive termination.") and a contract, and it is asked to classify whether each hypothesis is entailed by, contradicting to or not mentioned by (neutral to) the contract as well as identifying evidence for the decision as spans in the contract. Please refer our paper in "Findings of EMNLP 2021" and the dataset repository for the details of the task.

This repository maintains Span NLI BERT, a strong baseline for ContractNLI. It (1) makes the problem of evidence identification easier by modeling the problem as multi-label classification over spans instead of trying to predict the start and end tokens, and (b) introduces more sophisticated context segmentation to deal with long documents. We showed in our paper that Span NLI BERT significantly outperforms the existing models.

Usage

Dataset

Clone the repository to your desired directory. Download the dataset from the dataset repository and unzip JSON files to ./data/ directory (you may specify a custom dataset path by modifying a configuration file).

Prerequisite

Set up a CUDA environment. We used CUDA 11.1.1, cuDNN 8.0.5, NCCL 2.7.8-1 and GCC 7.4.0 in our experiments.

You need Python 3.8+ to run the codes. We used Python 3.8.5 in our experiments.

Install requirements with Pip.

pip install -r requirements.txt

If you want to use A100 GPUs as we did in our experiments, you may need to install PyTorch manually (not reflected in requirements.txt).

pip install torch==1.8.1+cu111 torchvision==0.9.1+cu111 torchaudio==0.8.1 -f https://download.pytorch.org/whl/torch_stable.html

Running experiments

You can run an experiment by feeding train.py an experiment configuration YAML file and specifying an output directory.

python train.py ./data/conf_base.yml ./output

Reproducibility

We have tagged the implementations that we used for the experiments in our paper. Please note that we have changed NLI label name since the experiments. You may need to alter "Entailment" to "true", "Contradiction" to "false" and "NotMentioned" to "na" in the dataset JSON files, or apply commit b0c4987 as a patch.

We carried out the experiments on ABCI, a GPU cluster with a PBS-like job queue. While it would not run in most users' environment, we provide our experiment procedure so that users can implement a similar procedure for their clusters.

# Generate configuration files in ./params
python gen_params.py data/param_tmpl.py 100 ./params

# Run tuning
./run_tuning.sh -s 1 -n 10 ${SECRET_GROUP_ID} ./params ./results

# Pick 3 models with the best validation macro NLI accuracies and report the average
python aggregate_results.py -n 3 -m macro_label_micro_doc.class.accuracy -o aggregated_metrics.txt ./results

License

Our dataset is released under Apache 2.0. Please refer attached "LICENSE" for the exact terms.

This implementation has partially been derived from Huggingface's implementation of SQuAD BERT. Please refer the commit log for the full changes.

When you use Span NLI BERT in your work, please cite our paper:

@inproceedings{koreeda-manning-2021-contractnli,
    title = "ContractNLI: A Dataset for Document-level Natural Language Inference for Contracts",
    author = "Koreeda, Yuta  and
      Manning, Christopher D.",
    booktitle = "Findings of the Association for Computational Linguistics: EMNLP 2021",
    year = "2021",
    publisher = "Association for Computational Linguistics"
}