UTagger: A Grounded Unsupervised Universal Part-of-Speech Tagger for Low-Resource Languages

This reposity contains the code neccesary to reproduce the results in the paper:

[1] A Grounded Unsupervised Universal Part-of-Speech Tagger for Low-Resource Languages. Ronald Cardenas, Ying Lin, Heng Ji and Jonathan May. NAACL 2019, Minneapolis, USA.

Requirements

Training of Language Models is done with SRILM v1.7.2. However, any library that produces an ARPA file can be used.

For FST manipulation and cipher training, we use Carmel (included as a submodule)

You will also need:

• Python 3.6
• NumPy >= 1.16.2
• SciPy >= 1.2.1
• lxml >= 4.3.3

Setup

Initialize the submodules as follows:

git submodule update --init --recursive

Then build the code in src/carmel, src/brown-cluster, and src/marlin (see each folder's README file for reference).

Using UTagger

0. Extract POS annotations from UniversalDependencies treebanks

If you want to use annoations from UD treebanks, you can extract the POS sequences by running

./setup_ud-treebank_data.sh -td <ud-treebank-parent-folder>

This will extract only the POS tags of CONLLU train files for languages experimented with in [1].

1. Train POS language models

• From UD data

Training for several languages can be done by listing the iso-639-1 code of each language separated by commas. For instance, to train second order LMs for English and German, run:

./train_format_lm_ud.sh  -l en,de  -o 2

• From POS token sequences (one sentence per line)

./train_srilm_langmodel.sh -i <pos-file> -o <order>

• Reformating an already trained LM in ARPA format

Further down in the pipeline, Carmel reads trained language models in OpenFST format. Reformat an ARPA file as follows:

./src/code/arpa2wfst.sh -i <arpa-file> -l <lang-id> -o <order>

2. Train UTagger

./utagger -i sample.in -if txt -m train \
-lm_o 2 -pl en,de -ca brown -nc 500

3. Tag / eval

./utagger -i sample.in -if txt -m tag \
-lm_o 2 -pl en,de -ca brown -nc 500