Yukyung Lee
Author directory2026
PGMem: Tightly Coupled Persona–Memory Graph for Lifelong Personalized Agents
Wonjun Choi | Yerim Kim | Yukyung Lee | Susik Yoon
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Wonjun Choi | Yerim Kim | Yukyung Lee | Susik Yoon
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Long-term personalized dialogue agents must track user preferences as their personas evolve. Existing memory systems organize past events well, but store personas as flat profiles detached from the events that justify them. This loose coupling leads to the memory–persona validity gap and the persona-aware retrieval gap. We propose PGMem, a heterogeneous persona-memory graph that connects event and persona nodes through typed provenance and evidence edges, keeping each persona signal traceable to the events that support or revise it. At retrieval time, PGMem expands from query-relevant seeds and ranks signals by evidential validity. Across three benchmarks with small language model backbones, PGMem consistently outperforms summary-based, persona-aware, graph-structured, and agentic memory baselines, and improves performance as the context grows. The source codes of PGMem are available at https://github.com/wonjunchoi23/pgmem/
AI Writers Have a Consistent Stylometric Footprint, but AI Editors Do Not
Zhengyang Shan | Yukyung Lee | Sophie Hao
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Zhengyang Shan | Yukyung Lee | Sophie Hao
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Text generated by large language models (LLMs) has been shown to be stylometrically distinct from human-written text (CITATION). But LLMs are increasingly used not only to generate text but also to edit human writing, and it is unclear whether the two leave the same trace. We show that AI generation leaves a consistent ”stylometric footprint”: a small subset of features, primarily entropy and lexical diversity, consistently separates AI-generated text from human writing across 8 LLMs and 5 domains, while the remaining features depend heavily on the domain and generator. AI editing, however, does not reproduce the same footprint. Relative to their human-written sources, AI-edited texts show only a small increase in lexical diversity and a decrease in entropy, rather than the joint increase that characterizes AI generation. Lexical density, which contributes little to generation, instead becomes the dominant editing-associated signal. Stylometric features therefore separate AI-edited text from AI-generated text but are substantially less effective at separating it from human-written text. Our results suggest that ”AI text” is not a single phenomenon: generation and editing leave qualitatively different stylometric traces and should be studied separately.
LLMs Learn Better In-Context from Rules than from Examples
Xiang Fu | Seungmin Cho | Yukyung Lee | Najoung Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Xiang Fu | Seungmin Cho | Yukyung Lee | Najoung Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Large language models (LLMs) exhibit in-context learning capabilities, where they can learn new tasks from prompt contexts without weight updates. We compare the learning efficacies of two prominent modes of in-context learning: (1) learning from descriptions of rules (instruction following); and (2) learning from examples of input-output demonstrations (few-shot prompting). Through five learning tasks that cover diverse domains (games, arithmetic, linguistic inferences), we compare two modes of learning (rules vs. examples) specifying the same underlying task. We furthermore explore model and task properties that modulate the learning efficacies. We find that models generally learn more reliably from rules than from examples alone, and additional examples on top of rules or simply scaling up the number of examples do not lead to consistent and significant gains. Instruction tuning amplifies the benefit of rule-based learning while keeping example-based learning capacities intact. Surprisingly, we find no privileged effect of example-based learning in base models, and rules still lead to gains in algebraic task domains. Overall, the comparative efficacy of rules over examples is larger when the task recruits algebraic abstractions and computations, and smaller when the task requires distributional sensitivity and/or recruits parametric knowledge.
RExBench: Can coding agents autonomously implement AI research extensions?
Nicholas Edwards | Yukyung Lee | Yujun Audrey Mao | Yulu Qin | Sebastian Schuster | Najoung Kim
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Nicholas Edwards | Yukyung Lee | Yujun Audrey Mao | Yulu Qin | Sebastian Schuster | Najoung Kim
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Agents based on Large Language Models (LLMs) have shown promise for performing sophisticated software engineering tasks autonomously. In addition, there has been progress towards developing agents that can perform parts of the research pipeline in machine learning and the natural sciences. We argue that research extension and its implementation is a critical capability for such systems, and introduce RExBench to support the evaluation of this capability. RExBench is a benchmark consisting of realistic extensions of 12 research papers that aim to investigate novel research hypotheses. Each task is set up as an extension to an existing research paper and codebase, accompanied by domain expert-written instructions. RExBench is robust to data contamination, and supports an automatic evaluation infrastructure that executes agent outputs to determine whether the success criteria are met. We use this benchmark to evaluate 12 LLM agents implemented using two different frameworks: aider and OpenHands. We find that all agents fail to autonomously implement the majority of the extensions, with the best agent at around 33% success rate. Although the success rate improves with additional human-written hints, the best performance under this setting remains below 44%. This indicates that current agents are still short of being able to handle realistic research extension tasks without substantial human guidance.
2025
Navigating the Path of Writing: Outline-guided Text Generation with Large Language Models
Yukyung Lee | Soonwon Ka | Bokyung Son | Pilsung Kang | Jaewook Kang
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 3: Industry Track)
Yukyung Lee | Soonwon Ka | Bokyung Son | Pilsung Kang | Jaewook Kang
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 3: Industry Track)
Large Language Models (LLMs) have impacted the writing process, enhancing productivity by collaborating with humans in content creation platforms. However, generating high-quality, user-aligned text to satisfy real-world content creation needs remains challenging. We propose WritingPath, a framework that uses explicit outlines to guide LLMs in generating goal-oriented, high-quality text. Our approach draws inspiration from structured writing planning and reasoning paths, focusing on reflecting user intentions throughout the writing process. To validate our approach in real-world scenarios, we construct a diverse dataset from unstructured blog posts to benchmark writing performance and introduce a comprehensive evaluation framework assessing the quality of outlines and generated texts. Our evaluations with various LLMs demonstrate that the WritingPath approach significantly enhances text quality according to evaluations by both LLMs and professional writers.
CheckEval: A reliable LLM-as-a-Judge framework for evaluating text generation using checklists
Yukyung Lee | JoongHoon Kim | Jaehee Kim | Hyowon Cho | Jaewook Kang | Pilsung Kang | Najoung Kim
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Yukyung Lee | JoongHoon Kim | Jaehee Kim | Hyowon Cho | Jaewook Kang | Pilsung Kang | Najoung Kim
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Existing LLM-as-a-Judge approaches for evaluating text generation suffer from rating inconsistencies, with low agreement and high rating variance across different evaluator models. We attribute this to subjective evaluation criteria combined with Likert scale scoring in existing protocols. To address this issue, we introduce CheckEval, a checklist-based evaluation framework that improves rating reliability via decomposed binary questions. Through experiments with 12 evaluator models across multiple datasets, we first demonstrate that CheckEval strongly correlates with human judgments. More importantly, CheckEval dramatically improves the average agreement across evaluator models by 0.45 and reduces the score variance. CheckEval scores furthermore have the benefit of being more interpretable because it decomposes evaluation criteria into traceable binary decisions, allowing analyses of specific attributes driving quality judgments.
2023
Painsight: An Extendable Opinion Mining Framework for Detecting Pain Points Based on Online Customer Reviews
Yukyung Lee | Jaehee Kim | Doyoon Kim | Yookyung Kho | Younsun Kim | Pilsung Kang
Proceedings of the 13th Workshop on Computational Approaches to Subjectivity, Sentiment, & Social Media Analysis
Yukyung Lee | Jaehee Kim | Doyoon Kim | Yookyung Kho | Younsun Kim | Pilsung Kang
Proceedings of the 13th Workshop on Computational Approaches to Subjectivity, Sentiment, & Social Media Analysis
As the e-commerce market continues to expand and online transactions proliferate, customer reviews have emerged as a critical element in shaping the purchasing decisions of prospective buyers. Previous studies have endeavored to identify key aspects of customer reviews through the development of sentiment analysis models and topic models. However, extracting specific dissatisfaction factors remains a challenging task. In this study, we delineate the pain point detection problem and propose Painsight, an unsupervised framework for automatically extracting distinct dissatisfaction factors from customer reviews without relying on ground truth labels. Painsight employs pre-trained language models to construct sentiment analysis and topic models, leveraging attribution scores derived from model gradients to extract dissatisfaction factors. Upon application of the proposed methodology to customer review data spanning five product categories, we successfully identified and categorized dissatisfaction factors within each group, as well as isolated factors for each type. Notably, Painsight outperformed benchmark methods, achieving substantial performance enhancements and exceptional results in human evaluations.
2022
Oh My Mistake!: Toward Realistic Dialogue State Tracking including Turnback Utterances
Takyoung Kim | Yukyung Lee | Hoonsang Yoon | Pilsung Kang | Junseong Bang | Misuk Kim
Proceedings of the Towards Semi-Supervised and Reinforced Task-Oriented Dialog Systems (SereTOD)
Takyoung Kim | Yukyung Lee | Hoonsang Yoon | Pilsung Kang | Junseong Bang | Misuk Kim
Proceedings of the Towards Semi-Supervised and Reinforced Task-Oriented Dialog Systems (SereTOD)
The primary purpose of dialogue state tracking(DST), a critical component of an end-toend conversational system, is to build a model that responds well to real-world situations. Although we often change our minds from time to time during ordinary conversations, current benchmark datasets do not adequately reflect such occurrences and instead consist of over-simplified conversations, in which no one changes their mind during a conversation. As the main question inspiring the present study, “Are current benchmark datasets sufficiently diverse to handle casual conversations in which one changes their mind after a certain topic is over?” We found that the answer is “No” because DST models cannot refer to previous user preferences when template-based turnback utterances are injected into the dataset. Even in the the simplest mind-changing (turnback) scenario, the performance of DST models significantly degenerated. However, we found that this performance degeneration can be recovered when the turnback scenarios are explicitly designed in the training set, implying that the problem is not with the DST models but rather with the construction of the benchmark dataset.
Mismatch between Multi-turn Dialogue and its Evaluation Metric in Dialogue State Tracking
Takyoung Kim | Hoonsang Yoon | Yukyung Lee | Pilsung Kang | Misuk Kim
Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)
Takyoung Kim | Hoonsang Yoon | Yukyung Lee | Pilsung Kang | Misuk Kim
Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)
Dialogue state tracking (DST) aims to extract essential information from multi-turn dialog situations and take appropriate actions. A belief state, one of the core pieces of information, refers to the subject and its specific content, and appears in the form of domain-slot-value. The trained model predicts “accumulated” belief states in every turn, and joint goal accuracy and slot accuracy are mainly used to evaluate the prediction; however, we specify that the current evaluation metrics have a critical limitation when evaluating belief states accumulated as the dialogue proceeds, especially in the most used MultiWOZ dataset. Additionally, we propose relative slot accuracy to complement existing metrics. Relative slot accuracy does not depend on the number of predefined slots, and allows intuitive evaluation by assigning relative scores according to the turn of each dialog. This study also encourages not solely the reporting of joint goal accuracy, but also various complementary metrics in DST tasks for the sake of a realistic evaluation.
2020
Multiˆ2OIE: Multilingual Open Information Extraction Based on Multi-Head Attention with BERT
Youngbin Ro | Yukyung Lee | Pilsung Kang
Findings of the Association for Computational Linguistics: EMNLP 2020
Youngbin Ro | Yukyung Lee | Pilsung Kang
Findings of the Association for Computational Linguistics: EMNLP 2020
In this paper, we propose Multi2OIE, which performs open information extraction (open IE) by combining BERT with multi-head attention. Our model is a sequence-labeling system with an efficient and effective argument extraction method. We use a query, key, and value setting inspired by the Multimodal Transformer to replace the previously used bidirectional long short-term memory architecture with multi-head attention. Multi2OIE outperforms existing sequence-labeling systems with high computational efficiency on two benchmark evaluation datasets, Re-OIE2016 and CaRB. Additionally, we apply the proposed method to multilingual open IE using multilingual BERT. Experimental results on new benchmark datasets introduced for two languages (Spanish and Portuguese) demonstrate that our model outperforms other multilingual systems without training data for the target languages.
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Co-authors
- Pilsung Kang 6
- Najoung Kim 3
- Jaewook Kang 2
- Jaehee Kim 2
- Misuk Kim 2
- Takyoung Kim 2
- Hoonsang Yoon 2
- Junseong Bang 1
- Hyowon Cho 1
- Seungmin Cho 1
- Wonjun Choi 1
- Nicholas Edwards 1
- Xiang Fu 1
- Sophie Hao 1
- Soonwon Ka 1
- Yookyung Kho 1
- Doyoon Kim 1
- JoongHoon Kim 1
- Yerim Kim 1
- Younsun Kim 1
- Yujun Audrey Mao 1
- Yulu Qin 1
- Youngbin Ro 1
- Sebastian Schuster 1
- Zhengyang Shan 1
- Bokyung Son 1
- Susik Yoon 1