Yi Lu


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TextObfuscator: Making Pre-trained Language Model a Privacy Protector via Obfuscating Word Representations
Xin Zhou | Yi Lu | Ruotian Ma | Tao Gui | Yuran Wang | Yong Ding | Yibo Zhang | Qi Zhang | Xuanjing Huang
Findings of the Association for Computational Linguistics: ACL 2023

In real-world applications, pre-trained language models are typically deployed on the cloud, allowing clients to upload data and perform compute-intensive inference remotely. To avoid sharing sensitive data directly with service providers, clients can upload numerical representations rather than plain text to the cloud. However, recent text reconstruction techniques have demonstrated that it is possible to transform representations into original words, suggesting that privacy risk remains. In this paper, we propose TextObfuscator, a novel framework for protecting inference privacy by applying random perturbations to clustered representations. The random perturbations make the representations indistinguishable from surrounding clustered representations, thus obscuring word information while retaining the original word functionality. To achieve this, we utilize prototypes to learn clustered representation, where tokens of similar functionality are encouraged to be closer to the same prototype during training. Additionally, we design different methods to find prototypes for token-level and sentence-level tasks, which can improve performance by incorporating semantic and task information. Experimental results on token and sentence classification tasks show that TextObfuscator achieves improvement over compared methods without increasing inference cost.

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Nonparametric Decoding for Generative Retrieval
Hyunji Lee | JaeYoung Kim | Hoyeon Chang | Hanseok Oh | Sohee Yang | Vladimir Karpukhin | Yi Lu | Minjoon Seo
Findings of the Association for Computational Linguistics: ACL 2023

The generative retrieval model depends solely on the information encoded in its model parameters without external memory, its information capacity is limited and fixed. To overcome the limitation, we propose Nonparametric Decoding (Np Decoding) which can be applied to existing generative retrieval models. Np Decoding uses nonparametric contextualized vocab embeddings (external memory) rather than vanilla vocab embeddings as decoder vocab embeddings. By leveraging the contextualized vocab embeddings, the generative retrieval model is able to utilize both the parametric and nonparametric space. Evaluation over 9 datasets (8 single-hop and 1 multi-hop) in the document retrieval task shows that applying Np Decoding to generative retrieval models significantly improves the performance. We also show that Np Decoding is data- and parameter-efficient, and shows high performance in the zero-shot setting.

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TextMixer: Mixing Multiple Inputs for Privacy-Preserving Inference
Xin Zhou | Yi Lu | Ruotian Ma | Tao Gui | Qi Zhang | Xuanjing Huang
Findings of the Association for Computational Linguistics: EMNLP 2023

Pre-trained language models (PLMs) are often deployed as cloud services, enabling users to upload textual data and perform inference remotely. However, users’ personal text often contains sensitive information, and sharing such data directly with the service providers can lead to serious privacy leakage. To address this problem, we introduce a novel privacy-preserving inference framework called MixPi , which prevents plaintext leakage during the inference phase. Inspired by k-anonymity, MixPi aims to obfuscate a user’s private input by mixing it with multiple other inputs, thereby confounding potential privacy attackers. To achieve this, our approach involves: (1) proposing a novel encryption module, Privacy Mixer, which encrypts input from three distinct dimensions: mixing, representation, and position. (2) adopting a pre-trained Multi-input Multi-output network to handle mixed representations and obtain multiple predictions. (3) employing a Privacy Demixer to ensure only the user can decrypt the real output among the multiple predictions. Furthermore, we explore different ways to automatically generate synthetic inputs required for mixing. Experimental results on token and sentence classification tasks demonstrate that MixPi greatly surpasses existing privacy-preserving methods in both performance and privacy.


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Improved Knowledge Distillation for Pre-trained Language Models via Knowledge Selection
Chenglong Wang | Yi Lu | Yongyu Mu | Yimin Hu | Tong Xiao | Jingbo Zhu
Findings of the Association for Computational Linguistics: EMNLP 2022

Knowledge distillation addresses the problem of transferring knowledge from a teacher model to a student model. In this process, we typically have multiple types of knowledge extracted from the teacher model. The problem is to make full use of them to train the student model. Our preliminary study shows that: (1) not all of the knowledge is necessary for learning a good student model, and (2) knowledge distillation can benefit from certain knowledge at different training steps. In response to these, we propose an actor-critic approach to selecting appropriate knowledge to transfer during the process of knowledge distillation. In addition, we offer a refinement of the training algorithm to ease the computational burden. Experimental results on the GLUE datasets show that our method outperforms several strong knowledge distillation baselines significantly.


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On the Transferability of Minimal Prediction Preserving Inputs in Question Answering
Shayne Longpre | Yi Lu | Chris DuBois
Proceedings of the 2021 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies

Recent work (Feng et al., 2018) establishes the presence of short, uninterpretable input fragments that yield high confidence and accuracy in neural models. We refer to these as Minimal Prediction Preserving Inputs (MPPIs). In the context of question answering, we investigate competing hypotheses for the existence of MPPIs, including poor posterior calibration of neural models, lack of pretraining, and “dataset bias” (where a model learns to attend to spurious, non-generalizable cues in the training data). We discover a perplexing invariance of MPPIs to random training seed, model architecture, pretraining, and training domain. MPPIs demonstrate remarkable transferability across domains achieving significantly higher performance than comparably short queries. Additionally, penalizing over-confidence on MPPIs fails to improve either generalization or adversarial robustness. These results suggest the interpretability of MPPIs is insufficient to characterize generalization capacity of these models. We hope this focused investigation encourages more systematic analysis of model behavior outside of the human interpretable distribution of examples.

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MKQA: A Linguistically Diverse Benchmark for Multilingual Open Domain Question Answering
Shayne Longpre | Yi Lu | Joachim Daiber
Transactions of the Association for Computational Linguistics, Volume 9

Progress in cross-lingual modeling depends on challenging, realistic, and diverse evaluation sets. We introduce Multilingual Knowledge Questions and Answers (MKQA), an open- domain question answering evaluation set comprising 10k question-answer pairs aligned across 26 typologically diverse languages (260k question-answer pairs in total). Answers are based on heavily curated, language- independent data representation, making results comparable across languages and independent of language-specific passages. With 26 languages, this dataset supplies the widest range of languages to-date for evaluating question answering. We benchmark a variety of state- of-the-art methods and baselines for generative and extractive question answering, trained on Natural Questions, in zero shot and translation settings. Results indicate this dataset is challenging even in English, but especially in low-resource languages.1


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基於圖神經網路之中文健康照護命名實體辨識 (Chinese Healthcare Named Entity Recognition Based on Graph Neural Networks)
Yi Lu | Lung-Hao Lee
International Journal of Computational Linguistics & Chinese Language Processing, Volume 25, Number 2, December 2020

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Gated Graph Sequence Neural Networks for Chinese Healthcare Named Entity Recognition
Yi Lu | Lung-Hao Lee
Proceedings of the 32nd Conference on Computational Linguistics and Speech Processing (ROCLING 2020)


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NCUEE at MEDIQA 2019: Medical Text Inference Using Ensemble BERT-BiLSTM-Attention Model
Lung-Hao Lee | Yi Lu | Po-Han Chen | Po-Lei Lee | Kuo-Kai Shyu
Proceedings of the 18th BioNLP Workshop and Shared Task

This study describes the model design of the NCUEE system for the MEDIQA challenge at the ACL-BioNLP 2019 workshop. We use the BERT (Bidirectional Encoder Representations from Transformers) as the word embedding method to integrate the BiLSTM (Bidirectional Long Short-Term Memory) network with an attention mechanism for medical text inferences. A total of 42 teams participated in natural language inference task at MEDIQA 2019. Our best accuracy score of 0.84 ranked the top-third among all submissions in the leaderboard.

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An Exploration of Data Augmentation and Sampling Techniques for Domain-Agnostic Question Answering
Shayne Longpre | Yi Lu | Zhucheng Tu | Chris DuBois
Proceedings of the 2nd Workshop on Machine Reading for Question Answering

To produce a domain-agnostic question answering model for the Machine Reading Question Answering (MRQA) 2019 Shared Task, we investigate the relative benefits of large pre-trained language models, various data sampling strategies, as well as query and context paraphrases generated by back-translation. We find a simple negative sampling technique to be particularly effective, even though it is typically used for datasets that include unanswerable questions, such as SQuAD 2.0. When applied in conjunction with per-domain sampling, our XLNet (Yang et al., 2019)-based submission achieved the second best Exact Match and F1 in the MRQA leaderboard competition.


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Factored Statistical Machine Translation for Grammatical Error Correction
Yiming Wang | Longyue Wang | Xiaodong Zeng | Derek F. Wong | Lidia S. Chao | Yi Lu
Proceedings of the Eighteenth Conference on Computational Natural Language Learning: Shared Task

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Domain Adaptation for Medical Text Translation using Web Resources
Yi Lu | Longyue Wang | Derek F. Wong | Lidia S. Chao | Yiming Wang
Proceedings of the Ninth Workshop on Statistical Machine Translation

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Combining Domain Adaptation Approaches for Medical Text Translation
Longyue Wang | Yi Lu | Derek F. Wong | Lidia S. Chao | Yiming Wang | Francisco Oliveira
Proceedings of the Ninth Workshop on Statistical Machine Translation

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UM-Corpus: A Large English-Chinese Parallel Corpus for Statistical Machine Translation
Liang Tian | Derek F. Wong | Lidia S. Chao | Paulo Quaresma | Francisco Oliveira | Yi Lu | Shuo Li | Yiming Wang | Longyue Wang
Proceedings of the Ninth International Conference on Language Resources and Evaluation (LREC'14)

Parallel corpus is a valuable resource for cross-language information retrieval and data-driven natural language processing systems, especially for Statistical Machine Translation (SMT). However, most existing parallel corpora to Chinese are subject to in-house use, while others are domain specific and limited in size. To a certain degree, this limits the SMT research. This paper describes the acquisition of a large scale and high quality parallel corpora for English and Chinese. The corpora constructed in this paper contain about 15 million English-Chinese (E-C) parallel sentences, and more than 2 million training data and 5,000 testing sentences are made publicly available. Different from previous work, the corpus is designed to embrace eight different domains. Some of them are further categorized into different topics. The corpus will be released to the research community, which is available at the NLP2CT website.


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Language-independent Model for Machine Translation Evaluation with Reinforced Factors
Aaron Li-Feng Han | Derek F. Wong | Lidia S. Chao | Liangye He | Yi Lu | Junwen Xing | Xiaodong Zeng
Proceedings of Machine Translation Summit XIV: Posters

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Edit Distance: A New Data Selection Criterion for Domain Adaptation in SMT
Longyue Wang | Derek F. Wong | Lidia S. Chao | Junwen Xing | Yi Lu | Isabel Trancoso
Proceedings of the International Conference Recent Advances in Natural Language Processing RANLP 2013

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Entity Linking for Tweets
Xiaohua Liu | Yitong Li | Haocheng Wu | Ming Zhou | Furu Wei | Yi Lu
Proceedings of the 51st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)

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Quality Estimation for Machine Translation Using the Joint Method of Evaluation Criteria and Statistical Modeling
Aaron Li-Feng Han | Yi Lu | Derek F. Wong | Lidia S. Chao | Liangye He | Junwen Xing
Proceedings of the Eighth Workshop on Statistical Machine Translation

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A Description of Tunable Machine Translation Evaluation Systems in WMT13 Metrics Task
Aaron Li-Feng Han | Derek F. Wong | Lidia S. Chao | Yi Lu | Liangye He | Yiming Wang | Jiaji Zhou
Proceedings of the Eighth Workshop on Statistical Machine Translation