policy-classifier

This repository aims to reproduce a Random Forests privacy-policy classifier which was originally described in the Princeton-Leuven Longitudinal Corpus of Privacy Policies paper. We train our classifier on TF-IDF text features from annotated privacy-policy markdown documents released alongside the aforementioned publication.

Our classifier was trained on a randomly split training set using a hyperparameter grid-search and 5-fold cross validation. It achieved a mean test ROC-AUC score of 0.955 during cross-validation. We then conducted post-hoc threshold tuning on a holdout set and found that a threshold of 0.752 was required to reach a precision of 0.99 for the privacy-policy or positive label. Finally after threshold tuning, we trained our classifier with the best performing hyperparameters on all training data to produce a production-ready model.

The final model can be found as a Git LFS object in the policy-classifier-data repository.

Dependencies 🔍

1. This repository's code was tested with Python version 3.8.12. We recommend creating a virtual environment with the same python version and installing dependencies with poetry:

   $ poetry install
   

   Alternatively, install dependencies in the virtual environment using pip:

   $ pip install -r requirements.txt
   

2. Optional: To further develop this repository, install pre-commit to setup pre-commit hooks for code-checks.

Initialization 🔥

1. To download and prepare annotated privacy-policies data for training, simply execute:

   $ bash scripts/prepare.sh
   

2. Optional: To install pre-commit hooks for further development of this repository, execute:

   $ pre-commit install
   

Usage ❄️

Train

usage: train.py [-h] [--cv-splits <int>] [--debug]
                [--logging-level {DEBUG,INFO,WARNING,ERROR,CRITICAL}]
                [--n-jobs <int>] [--policies-csv <file_path>]
                [--precision-threshold <float>] [--random-seed <int>]
                [--scoring <str>]

optional arguments:
  --cv-splits            <int>
                         number of cross-validation splits (default: 5)
  --debug                flag to debug script (default: False)
  --logging-level        {DEBUG,INFO,WARNING,ERROR,CRITICAL}
                         set logging level (default: INFO)
  --n-jobs               <int>
                         number of parallel jobs, specify -1 to use all processors
                         (default: 1)
  --policies-csv         <file_path>
                         path to gold policies csv file (default:
                         data/1301_dataset.csv)
  --precision-threshold  <float>
                         precision threshold to match (default: 0.99)
  --random-seed          <int>
                         global random seed for RNGs (default: 42)
  --scoring              <str>
                         scoring metric for GridSearchCV (default: roc_auc)
  -h, --help             show this help message and exit

In order to train, cross-validate and evaluate the model, simply execute:

$ python3 src/train.py

This workflow will create a run directory in ./runs and will dump all necessary logs, metrics and the final model checkpoint as a dill pickle. The dumped model checkpoint is a sklearn pipeline containing the TfidfVectorizer and RandomForestClassifier classes.

Predict

In order to use a dumped model for downstream tasks, it is necessary to set up a virtual environment with the same Python and Scikit-Learn versions as this repository. Not doing so could result in unforeseen errors during the unpickling phase. Below is a code-snippet documenting how to import and use the best saved model for prediction:

# load necessary dependencies
from dill import load

# load the model as stream of bytes
with open("path/to/model.dill", "rb") as input_file_stream:
    model = load(input_file_stream)

# predict and provide probabilities for text being a privacy policy
model.predict_proba(["some markdown text", "some policy text"])[:,1]

Test 🔬

To run unit and integration tests, execute:

$ pytest

Citation 📖

If you found this repository helpful, we kindly ask you to cite our publication titled Privacy and Customer’s Education: NLP for Information Resources Suggestions and Expert Finder Systems:

@InProceedings{10.1007/978-3-031-05563-8_5,
  author =       "Mazzola, Luca and Waldis, Andreas and Shankar, Atreya and
                  Argyris, Diamantis and Denzler, Alexander and Van Roey,
                  Michiel",
  editor =       "Moallem, Abbas",
  title =        "Privacy and Customer's Education: NLP for Information
                  Resources Suggestions and Expert Finder Systems",
  booktitle =    "HCI for Cybersecurity, Privacy and Trust",
  year =         "2022",
  publisher =    "Springer International Publishing",
  address =      "Cham",
  pages =        "62--77",
  isbn =         "978-3-031-05563-8"
}