Hyungtak Choi


2022

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Multi-Domain Dialogue State Tracking By Neural-Retrieval Augmentation
Lohith Ravuru | Seonghan Ryu | Hyungtak Choi | Haehun Yang | Hyeonmok Ko
Findings of the Association for Computational Linguistics: AACL-IJCNLP 2022

Dialogue State Tracking (DST) is a very complex task that requires precise understanding and information tracking of multi-domain conversations between users and dialogue systems. Many task-oriented dialogue systems use dialogue state tracking technology to infer users’ goals from the history of the conversation. Existing approaches for DST are usually conditioned on previous dialogue states. However, the dependency on previous dialogues makes it very challenging to prevent error propagation to subsequent turns of a dialogue. In this paper, we propose Neural Retrieval Augmentation to alleviate this problem by creating a Neural Index based on dialogue context. Our NRA-DST framework efficiently retrieves dialogue context from the index built using a combination of unstructured dialogue state and structured user/system utterances. We explore a simple pipeline resulting in a retrieval-guided generation approach for training a DST model. Experiments on different retrieval methods for augmentation show that neural retrieval augmentation is the best performing retrieval method for DST. Our evaluations on the large-scale MultiWOZ dataset show that our model outperforms the baseline approaches.

2020

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An Empirical Study on Multi-Task Learning for Text Style Transfer and Paraphrase Generation
Pawel Bujnowski | Kseniia Ryzhova | Hyungtak Choi | Katarzyna Witkowska | Jaroslaw Piersa | Tymoteusz Krumholc | Katarzyna Beksa
Proceedings of the 28th International Conference on Computational Linguistics: Industry Track

The topic of this paper is neural multi-task training for text style transfer. We present an efficient method for neutral-to-style transformation using the transformer framework. We demonstrate how to prepare a robust model utilizing large paraphrases corpora together with a small parallel style transfer corpus. We study how much style transfer data is needed for a model on the example of two transformations: neutral-to-cute on internal corpus and modern-to-antique on publicly available Bible corpora. Additionally, we propose a synthetic measure for the automatic evaluation of style transfer models. We hope our research is a step towards replacing common but limited rule-based style transfer systems by more flexible machine learning models for both public and commercial usage.

2019

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VAE-PGN based Abstractive Model in Multi-stage Architecture for Text Summarization
Hyungtak Choi | Lohith Ravuru | Tomasz Dryjański | Sunghan Rye | Donghyun Lee | Hojung Lee | Inchul Hwang
Proceedings of the 12th International Conference on Natural Language Generation

This paper describes our submission to the TL;DR challenge. Neural abstractive summarization models have been successful in generating fluent and consistent summaries with advancements like the copy (Pointer-generator) and coverage mechanisms. However, these models suffer from their extractive nature as they learn to copy words from the source text. In this paper, we propose a novel abstractive model based on Variational Autoencoder (VAE) to address this issue. We also propose a Unified Summarization Framework for the generation of summaries. Our model eliminates non-critical information at a sentence-level with an extractive summarization module and generates the summary word by word using an abstractive summarization module. To implement our framework, we combine submodules with state-of-the-art techniques including Pointer-Generator Network (PGN) and BERT while also using our new VAE-PGN abstractive model. We evaluate our model on the benchmark Reddit corpus as part of the TL;DR challenge and show that our model outperforms the baseline in ROUGE score while generating diverse summaries.

2018

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Self-Learning Architecture for Natural Language Generation
Hyungtak Choi | Siddarth K.M. | Haehun Yang | Heesik Jeon | Inchul Hwang | Jihie Kim
Proceedings of the 11th International Conference on Natural Language Generation

In this paper, we propose a self-learning architecture for generating natural language templates for conversational assistants. Generating templates to cover all the combinations of slots in an intent is time consuming and labor-intensive. We examine three different models based on our proposed architecture - Rule-based model, Sequence-to-Sequence (Seq2Seq) model and Semantically Conditioned LSTM (SC-LSTM) model for the IoT domain - to reduce the human labor required for template generation. We demonstrate the feasibility of template generation for the IoT domain using our self-learning architecture. In both automatic and human evaluation, the self-learning architecture outperforms previous works trained with a fully human-labeled dataset. This is promising for commercial conversational assistant solutions.