Roles of MLLMs in Visually Rich Document Retrieval for RAG: A Survey
On the map: Retrieval-augmented generation → Multimodal RAG
Abstract (arXiv)
Visually rich documents (VRDs) challenge retrieval-augmented generation (RAG) with layout-dependent semantics, brittle OCR, and evidence spread across complex figures and structured tables. This survey examines how Multimodal Large Language Models (MLLMs) are being used to make VRD retrieval practical for RAG. We organize the literature into three roles: Modality-Unifying Captioners, Multimodal Embedders, and End-to-End Representers. We compare these roles along retrieval granularity, information fidelity, latency and index size, and compatibility with reranking and grounding. We also outline key trade-offs and offer some practical guidance on when to favor each role. Finally, we identify promising directions for future research, including adaptive retrieval units, model size reduction, and the development of evaluation methods.
Key facts. Cited by 2 papers in the map (data through 7 Oct 2026). Placed in Multimodal RAG, one of 15 directions in Retrieval-augmented generation. Builds on 93 of its 125 references that are in the map. First posted on arXiv 16 Dec 2025.
Builds on
93 of 125 references.
Closest ancestors · 16
Same direction, newest first
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- 2022REVEAL: Retrieval-Augmented Visual-Language Pre-Training with Multi-Source Multimodal Knowledge Memory10 Dec
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Other references · 77
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Citing papers per year: 2026: 2.
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