UNIDOC-BENCH: A Unified Benchmark for Document-Centric Multimodal RAG

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Main Authors: Peng, Xiangyu, Qin, Can, Chen, Zeyuan, Xu, Ran, Xiong, Caiming, Wu, Chien-Sheng
Format: Preprint
Published: 2025
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author Peng, Xiangyu
Qin, Can
Chen, Zeyuan
Xu, Ran
Xiong, Caiming
Wu, Chien-Sheng
author_facet Peng, Xiangyu
Qin, Can
Chen, Zeyuan
Xu, Ran
Xiong, Caiming
Wu, Chien-Sheng
contents Multimodal retrieval-augmented Generation (MM-RAG) is a key approach for applying large language models (LLMs) and agents to real-world knowledge bases, yet current evaluations are fragmented -- focusing on either text or images in isolation, or simplified multimodal setup, failing to capture document-centric multimodal use cases. In this paper, we introduce UniDoc-Bench, the first large-scale, realistic benchmark for MM-RAG built from $k$ real-world PDF pages across domains. Our pipeline extracts and links evidence from text, tables, and figures, then generates multimodal QA pairs spanning factual retrieval, comparison, summarization, and logical reasoning queries. To ensure reliability, all of QA pairs are validated by multiple human annotators and expert adjudication. UniDoc-Bench supports apples-to-apples comparison across four paradigms: 1) text-only, 2) image-only, 3) \emph{multimodal} text-image fusion and 4) multimodal joint retrieval -- under a unified protocol with standardized candidate pools, prompts, and evaluation metrics. UniDoc-Bench can also be used to evaluate Visual Question Answering (VQA) tasks. Our experiments show that multimodal text-image fusion RAG systems consistently outperform both unimodal and jointly multimodal embedding-based retrieval, indicating that neither text nor images alone are sufficient and that current multimodal embeddings remain inadequate. Beyond benchmarking, our analysis reveals when and how visual context complements textual evidence, uncovers systematic failure modes, and offers actionable guidance for developing more robust MM-RAG pipelines.
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id arxiv_https___arxiv_org_abs_2510_03663
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle UNIDOC-BENCH: A Unified Benchmark for Document-Centric Multimodal RAG
Peng, Xiangyu
Qin, Can
Chen, Zeyuan
Xu, Ran
Xiong, Caiming
Wu, Chien-Sheng
Computation and Language
Computer Vision and Pattern Recognition
Multimodal retrieval-augmented Generation (MM-RAG) is a key approach for applying large language models (LLMs) and agents to real-world knowledge bases, yet current evaluations are fragmented -- focusing on either text or images in isolation, or simplified multimodal setup, failing to capture document-centric multimodal use cases. In this paper, we introduce UniDoc-Bench, the first large-scale, realistic benchmark for MM-RAG built from $k$ real-world PDF pages across domains. Our pipeline extracts and links evidence from text, tables, and figures, then generates multimodal QA pairs spanning factual retrieval, comparison, summarization, and logical reasoning queries. To ensure reliability, all of QA pairs are validated by multiple human annotators and expert adjudication. UniDoc-Bench supports apples-to-apples comparison across four paradigms: 1) text-only, 2) image-only, 3) \emph{multimodal} text-image fusion and 4) multimodal joint retrieval -- under a unified protocol with standardized candidate pools, prompts, and evaluation metrics. UniDoc-Bench can also be used to evaluate Visual Question Answering (VQA) tasks. Our experiments show that multimodal text-image fusion RAG systems consistently outperform both unimodal and jointly multimodal embedding-based retrieval, indicating that neither text nor images alone are sufficient and that current multimodal embeddings remain inadequate. Beyond benchmarking, our analysis reveals when and how visual context complements textual evidence, uncovers systematic failure modes, and offers actionable guidance for developing more robust MM-RAG pipelines.
title UNIDOC-BENCH: A Unified Benchmark for Document-Centric Multimodal RAG
topic Computation and Language
Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2510.03663