Xiangyu Peng


2025

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Unanswerability Evaluation for Retrieval Augmented Generation
Xiangyu Peng | Prafulla Kumar Choubey | Caiming Xiong | Chien-Sheng Wu
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)

Existing evaluation frameworks for retrieval-augmented generation (RAG) systems focus on answerable queries, but they overlook the importance of appropriately rejecting unanswerable requests. In this paper, we introduce UAEval4RAG, a comprehensive evaluation framework designed to evaluate whether RAG systems effectively handle unanswerable queries specific to a given knowledge base. We first define a taxonomy with six unanswerable categories, and UAEval4RAG automatically synthesizes diverse and challenging queries for any given knowledge base and evaluate the RAG systems with unanswered ratio and acceptable ratio metrics. We also conduct experiments with various RAG components and prompting strategies across four datasets, which reveals that due to varying knowledge distribution across datasets, no single configuration consistently delivers optimal performance on both answerable and unanswerable requests across different knowledge bases. Our findings highlight the critical role of component selection and prompt design in optimizing RAG systems to balance the accuracy of answerable queries with high rejection rates of unanswerable ones. UAEval4RAG provides valuable insights and tools for developing more robust and reliable RAG systems.

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Turning Conversations into Workflows: A Framework to Extract and Evaluate Dialog Workflows for Service AI Agents
Prafulla Kumar Choubey | Xiangyu Peng | Shilpa Bhagavath | Caiming Xiong | Shiva Kumar Pentyala | Chien-Sheng Wu
Findings of the Association for Computational Linguistics: ACL 2025

Automated service agents require well-structured workflows to deliver consistent and accurate responses to customer queries. However, such workflows are often undocumented, and their automatic extraction from conversations remains largely unexplored. In this work, we present a novel framework for extracting and evaluating dialog workflows from historical interactions. Our extraction process involves two key stages: (1) a retrieval step to select relevant conversations based on key procedural elements, and (2) a structured workflow generation step using question-answer-based chain-of-thought (QA-CoT) prompting. To comprehensively evaluate the quality of the extracted workflows, we introduce an automated simulation framework with agent and customer bots that measures their effectiveness in resolving customer issues. Extensive experiments on the ABCD and SynthABCD datasets show that our QA-CoT technique improves workflow extraction by 12.16% in average macro accuracy over the baseline. Moreover, our evaluation method closely aligns with human assessments, offering a reliable and scalable framework for future research.

2024

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Automatic Bug Detection in LLM-Powered Text-Based Games Using LLMs
Claire Jin | Sudha Rao | Xiangyu Peng | Portia Botchway | Jessica Quaye | Chris Brockett | Bill Dolan
Findings of the Association for Computational Linguistics: ACL 2024

Advancements in large language models (LLMs) are revolutionizing interactive game design, enabling dynamic plotlines and interactions between players and non-player characters (NPCs). However, LLMs may exhibit flaws such as hallucinations, forgetfulness, or misinterpretations of prompts, causing logical inconsistencies and unexpected deviations from intended designs. Automated techniques for detecting such game bugs are still lacking. To address this, we propose a systematic LLM-based method for automatically identifying such bugs from player game logs, eliminating the need for collecting additional data such as post-play surveys. Applied to a text-based game DejaBoom!, our approach effectively identifies bugs inherent in LLM-powered interactive games, surpassing unstructured LLM-powered bug-catching methods and filling the gap in automated detection of logical and design flaws.

2022

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Inferring the Reader: Guiding Automated Story Generation with Commonsense Reasoning
Xiangyu Peng | Siyan Li | Sarah Wiegreffe | Mark Riedl
Findings of the Association for Computational Linguistics: EMNLP 2022

Transformer-based language model approaches to automated story generation currently provide state-of-the-art results. However, they still suffer from plot incoherence when generatingnarratives over time, and critically lack basiccommonsense reasoning. Furthermore, existing methods generally focus only on single-character stories, or fail to track charactersat all. To improve the coherence of generated narratives and to expand the scope ofcharacter-centric narrative generation, we introduce Commonsense-inference Augmentedneural StoryTelling (CAST), a framework forintroducing commonsense reasoning into thegeneration process with the option to model theinteraction between multiple characters. Wefind that our CAST method produces significantly more coherent, on-topic, enjoyable andfluent stories than existing models in both thesingle-character and two-character settings inthree storytelling domains.

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Guiding Neural Story Generation with Reader Models
Xiangyu Peng | Kaige Xie | Amal Alabdulkarim | Harshith Kayam | Samihan Dani | Mark Riedl
Findings of the Association for Computational Linguistics: EMNLP 2022

Automated storytelling has long captured the attention of researchers for the ubiquity of narratives in everyday life. However, it is challenging to maintain coherence and stay on-topictoward a specific ending when generating narratives with neural language models. In this paper, we introduce Story generation with ReaderModels (StoRM), a framework in which areader model is used to reason about the storyshould progress. A reader model infers whata human reader believes about the concepts,entities, and relations about the fictional storyworld. We show how an explicit reader modelrepresented as a knowledge graph affords the storycoherence and provides controllability in theform of achieving a given story world stategoal. Experiments show that our model produces significantly more coherent and on-topicstories, outperforming baselines in dimensionsincluding plot plausibility and staying on topic

2021

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Automatic Story Generation: Challenges and Attempts
Amal Alabdulkarim | Siyan Li | Xiangyu Peng
Proceedings of the Third Workshop on Narrative Understanding

Automated storytelling has long captured the attention of researchers for the ubiquity of narratives in everyday life. The best human-crafted stories exhibit coherent plot, strong characters, and adherence to genres, attributes that current states-of-the-art still struggle to produce, even using transformer architectures. In this paper, we analyze works in story generation that utilize machine learning approaches to (1) address story generation controllability, (2) incorporate commonsense knowledge, (3) infer reasonable character actions, and (4) generate creative language.

2020

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Reducing Non-Normative Text Generation from Language Models
Xiangyu Peng | Siyan Li | Spencer Frazier | Mark Riedl
Proceedings of the 13th International Conference on Natural Language Generation

Large-scale, transformer-based language models such as GPT-2 are pretrained on diverse corpora scraped from the internet. Consequently, they are prone to generating non-normative text (i.e. in violation of social norms). We introduce a technique for fine-tuning GPT-2, using a policy gradient reinforcement learning technique and a normative text classifier to produce reward and punishment values. We evaluate our technique on five data sets using automated and human participant experiments. The normative text classifier is 81-90% accurate when compared to gold-standard human judgements of normative and non-normative generated text. Our normative fine-tuning technique is able to reduce non-normative text by 27-61%, depending on the data set.