Retrieval-Augmented Generation for Large Language Models: A Survey

Large Language Models (LLMs) demonstrate significant capabilities but face challenges such as hallucination, outdated knowledge, and non-transparent, untraceable reasoning processes. Augmented Generation (RAG) has emerged as a promising solution to these issues by incorporating real-time data from external databases into LLM responses. This enhances the accuracy and credibility of the models, particularly for knowledge-intensive tasks, and allows for continuous knowledge updates and integration of domain-specific information. RAG synergistically merges LLMs' intrinsic knowledge with the vast, dynamic repositories of external databases. This survey paper provides an in-depth analysis of the evolution of RAG, focusing on three key paradigms: Naive RAG, Advanced RAG, and Modular RAG. It methodically examines the three fundamental components of RAG systems: the retriever, the generator, and the augmentation methods, underscoring the cutting-edge technologies within each componenet. Additionally, the paper introduces novel metrics and capabilities for evaluating RAG models, as well as the most recent evaluation framework. Finally, the paper outlines future research directions from three perspectives: future challenges,modality extension,and the development of the RAG technical stack and ecosystem