vietner: A Feature-based Vietnamese Named-Entity Recognition Model

Author: Pham Quang Nhat Minh

vietner is a feature-based named-entity recognition model that obtained very strong results on VLSP 2016 and VLSP 2018 NER data sets. In VLSP 2018 evaluation campaign, vietner obtained the first rank among participant systems.

Details of the model and features used in the model can be found in the following papers.

1. Pham Quang Nhat Minh (2018). A Feature-Rich Vietnamese Named-Entity Recognition Model. arXiv preprint arXiv:1803.04375.
2. Pham, M. Q. N. (2018). A Feature-Based Model for Nested Named-Entity Recognition at VLSP-2018 NER Evaluation Campaign. Journal of Computer Science and Cybernetics, 34(4), 311-321. Link: http://www.vjs.ac.vn/index.php/jcc/article/view/13163

Requirements

• Python 3.6.3
• regex
• Perl (version 5)
• yaml
• pandas
• nltk
• crfsuite 0.12

Resources

In experiments on VLSP 2016 and VLSP 2018 NER data, we used following resources.

• glove vectors
• word2vec vectors
• Brown word clusters with 1000 clusters.
• Brown word clusters with 5120 clusters

Details of above resources can be found in the paper [1].

You can download above resources on this link. After downloading the resource file resources.zip, uncompress the file into the root directory of vietner directory.

Experimental results on VLSP 2016 data set

Go to the directory ./vlsp2016_exp and perform the shell script run.sh.

For the details see the README.md file the the directory vlsp2016_exp.

You may need to change the paths to training, test data, output directories in the shell scripts and configuration files in the directory ./vlsp2016_exp/config

Following table shows the experimental results with three settings:

• Using Original POS and chunking tags provided in the data. In this setting, we use all features derived from words, POS tags, chunking tags
• Without chunking tags: we use features derived from words and POS tags
• Without POS, chunking tags: we use only features derived from words

We use Precision, Recall, F1 as evaluation measures. These measures are calculated using the perl script conlleval.

Note: we modified some annotation mistakes in the training and test data (e.g., missing B- tags), so the following results may be different from the reported results in the paper [1].

Setting	Precision	Recall	F1
Original POS and chunking tags	93.68	94.03	93.85
Without chunking tags	90.13	90.49	90.31
Without POS, chunking tags	89.93	90.29	90.11

Experimental results on VLSP 2018 data set

See the README.md within the directory vlsp2018_exp for more details.

We report experimental results of three systems as follows. The evaluation measures were calculated by using the official evaluation program evaluation.jar that was provided by VLSP 2018 organizers. The program calculated Precision, Recall, F1 scores for all named entities including nested entities. We only reported overall evaluation without taking Domains into account.

• Joint: We use joint model to recognize joint tags for each token of a sequence, then split joint tags into level-1 and level-2 tags. This is the method used in the run 4 described in the paper [2].
• Hybrid: We use the joint model for recognizing level-2 entities and level-1 model for recognizing level-1 entities. This is the method used in the run 2 described in the paper [2].
• Separated: Using level-1 and level-2 model for recognizing level-1 and level-2 entities, respectively. This is the method used in the run 6 described in the paper [2].

Evaluation results of the official submissions (See the paper [2])

System	Precision	Recall	F1
Joint	77.99	71.1	74.70
Separated	78.35	70.44	74.19
Hybrid	78.32	70.88	74.41

Currently, our Joint system obtains SOTA F1 score on VLSP 2018 data set (including nested named entity recognition).

Note: the paper Dong and Nguyen, 2018. Attentive Neural Network for Named Entity Recognition in Vietnamese only reported the F1 score for one level of entities not including nested named entities. They did not handle nested named entities.

Citation

If you use vietner in your papers, please cite following papers.

@article{minh2018a,
  title={A Feature-Rich Vietnamese Named-Entity Recognition Model},
  author={Minh, Pham Quang Nhat},
  journal={Proceedings of CICLING 2018},
  year={2018}
}

@article{JCC13163,
    author = {Minh Pham},
    title = {A Feature-Based Model for Nested Named-Entity Recognition at VLSP-2018 NER Evaluation Campaign},
    journal = {Journal of Computer Science and Cybernetics},
    volume = {34},
    number = {4},
    year = {2019},
    keywords = {Nested named-entity recognition, CRF, VLSP},
    abstract = {In this report, we describe our participant named-entity recognition system at VLSP 2018 evaluation campaign. We formalized the task as a sequence labeling problem using BIO encoding scheme. We applied a feature-based model which combines word, word-shape features, Brown-cluster-based features, and word-embedding-based features. We compare several methods to deal with nested entities in the dataset. We showed that combining tags of entities at all levels for training a sequence labeling model (joint-tag model) improved the accuracy of nested named-entity recognition.},
    issn = {1813-9663}, pages = {311--321}, doi = {10.15625/1813-9663/34/4/13163},
    url = {http://www.vjs.ac.vn/index.php/jcc/article/view/13163}
}