What is RAG ?

What Is Retrieval-Augmented Generation (RAG), and Is It a Groundbreaking Way of Interacting with Historical Documents?

by Alvin Blackshear | Historian & Researcher

For as long as archives have existed, the historian's craft has depended on a single, stubborn skill: finding the right document among thousands of wrong ones. Card catalogs gave way to keyword search engines, which gave way to digitized finding aids, yet the underlying task never changed. A researcher formulates a question, searches a collection using the vocabulary available at the time, and hopes the terms they chose overlap with the terms an archivist or a scanner happened to preserve. Retrieval-Augmented Generation, or RAG, is the first technology in this long lineage that promises to close the gap between what a historian actually wants to know and what a search box is capable of returning. Whether it fully delivers on that promise, and under what conditions, is the question this article sets out to examine.

Why Historians Need RAG Rather Than a Generic Chatbot

It is tempting to assume that any large language model, given enough context, can answer historical questions competently. This assumption is mistaken, and understanding why is essential to understanding what RAG actually contributes.

A generic LLM answers from its training data, a fixed and often outdated snapshot of text scraped from the internet. It has no reliable way to point to a specific archival folder, newspaper issue, or census page as the source of its claim, and it has every incentive, structurally speaking, to produce a fluent and confident answer even when no such source exists in its memory. For a historian, whose entire discipline rests on the traceability of a claim back to a primary document, this is disqualifying. An answer without a citation is not history. It is a plausible-sounding guess.

RAG changes the architecture in a specific way. Instead of relying solely on what a model memorized during training, a RAG system retrieves relevant passages from an external, defined collection, be it a digitized newspaper archive, a set of scanned letters, or a database of military records, and then asks the language model to generate an answer grounded in those retrieved passages. The research group behind the paper "Improving Access to Historical Archives with Real-time RAG-based Systems," led by Stergios Konstantinidis and colleagues, demonstrates this architecture at scale, applying it to a Swiss newspaper archive of roughly half a million segments spanning nearly two and a half centuries. Their system pairs a semantic retrieval and reranking pipeline with grounded answer generation, which means the model's output is tethered to specific archival text rather than floating free of any documentary anchor. This is the essential difference that makes RAG, rather than an ordinary chatbot, the appropriate tool for archival research.

How RAG Differs from Conventional Archival Search

Traditional archival search tools, including many of the platforms libraries and museums have relied on for decades, are built on lexical matching. A researcher types a term, and the system returns documents containing that exact term or a close variant. This works reasonably well when the researcher already knows the vocabulary used by the source material, but historical vocabulary shifts constantly. Place names change. Institutional terminology evolves. Spelling was inconsistent long before anyone standardized it. A search for a term as it is understood today may simply miss a document that describes the same event using nineteenth-century phrasing.

RAG systems address this through semantic retrieval, which represents both the query and the archival text as vectors in a shared conceptual space, allowing the system to surface documents that are meaningfully related even when the wording differs substantially. A master's thesis from the University of Twente, authored by Gauri Bhatnagar and focused on the CLARIAH Media Suite, an audiovisual heritage collection, tested exactly this proposition with real humanities scholars and archival professionals. The study found that RAG genuinely helps with cross-lingual access and exploratory, interpretive queries that lexical search struggles with, but it also surfaced a critical limitation: the system performed well on factual retrieval and named-entity identification, while struggling with interpretive reasoning and the kind of complex synthesis that sits at the heart of humanities scholarship. In other words, RAG can help a historian find the needle, but it cannot yet be trusted to explain what the needle means within a broader historiographical argument.

A separate, more industry-facing piece published by Veridian Software, a company that builds digital newspaper and archive platforms, frames RAG in more practical terms for institutions considering adoption, describing it as a natural extension of the search tools archives already maintain rather than a wholesale replacement of them.

Common Failure Modes in Archival RAG Systems

No technology arrives without its own characteristic failures, and archival RAG is no exception. Several recurring problems deserve explicit attention from anyone applying these tools to historical research.

OCR errors.  Most archival text exists as scanned images that have been converted to machine-readable text through optical character recognition, a process that is notoriously imperfect on older, damaged, or low-quality print. The Konstantinidis paper directly measures this problem and reports that an LLM-based refinement step reduced character error rates by up to roughly forty-five percent and word error rates by close to sixty-one percent, compared to the raw OCR output. That is a substantial improvement, but it is not perfection, and any residual error can silently distort a retrieved passage or an answer built on top of it.

Incomplete retrieval.  Even the best semantic search will not surface every relevant document, particularly when a collection is heterogeneous or when relevant material uses unusual phrasing, an obscure genre, or a minority language. A RAG system that returns five confident-sounding sources may be quietly ignoring a sixth that contradicts them.

Provenance loss.  When a language model synthesizes multiple retrieved passages into a single fluent answer, it is easy for the boundary between one source and another to blur. A historian needs to know precisely which claim came from which document, on which page, from which collection. A system that merges sources into an undifferentiated paragraph has failed a basic archival standard even if every individual fact happens to be accurate.

Temporal confusion.  Archives frequently contain material spanning centuries, and a retrieval system optimized purely for topical similarity has no inherent understanding of chronological sequence. It is entirely possible for a RAG system to present an 1850s account and a 1950s retrospective as though they were contemporaneous, a mistake that would mislead any historian relying on the system's framing rather than checking dates independently.

Fabricated citations.  Perhaps the most consequential failure mode is the language model's tendency to generate a citation that looks correct in form, a plausible archive box number or a newspaper date, but does not correspond to any actual retrieved document. Even well-grounded RAG systems are not fully immune to this, especially when a query has no good answer in the underlying collection and the model is inclined to produce something anyway rather than admit the gap.

The Missing Piece: A Historian's Evaluation Standard

Here is where the existing research reveals a striking gap. Every technical paper reviewed for this article evaluates RAG systems using measures native to information retrieval and natural language processing: retrieval precision, recall, embedding quality, OCR accuracy, system latency, and hallucination rate. A recent survey of RAG evaluation methods by Aoran Gan catalogs this landscape comprehensively, and a companion technical guide from Toloka lays out practical metrics for groundedness and answer faithfulness. These are legitimate and necessary measures. But none of them ask the questions a professional historian actually asks when assessing whether a piece of evidence is trustworthy.

Did the system retrieve the most authoritative version of a source, or merely the most textually similar one? Did it note when retrieved evidence contradicted itself, or did it quietly favor the passage that supported a cleaner narrative? Did it preserve the chain of custody and provenance for each claim? Did it distinguish a primary account from a later secondary interpretation of that account? Did it respect the order of events rather than collapsing decades into an undifferentiated blend? Did it accurately synthesize material drawn from separate collections without conflating them? Did it acknowledge uncertainty where the evidence was genuinely ambiguous, rather than resolving that ambiguity for the sake of a tidy answer? And did it surface evidence that was difficult to find but still relevant, rather than defaulting to whatever ranked highest by similarity score?

This gap between technical evaluation and historiographical evaluation is the foundation for what can be called a Historian's AI Evaluation Framework, or HAIEF. Rather than asking whether a RAG system is efficient, HAIEF asks whether it is trustworthy by the standards the historical profession has used for generations: provenance, contextualization, chronology, corroboration, and transparency about uncertainty. A system might score extremely well on NDCG or answer-correctness metrics, the kind reported by Konstantinidis and colleagues, whose reranking pipeline improved NDCG@10 from roughly sixty-six percent to eighty-seven percent, and still fail a historian's basic sniff test if it cannot show its provenance trail or if it silently smooths over contradictory testimony.

Toward a Historian's Testing Framework

A workable HAIEF would need to translate these five values into repeatable, scorable tests. Provenance could be scored by checking whether every claim in a generated answer links back to a specific, verifiable source with collection, folder, and page-level detail. Contextualization could be scored by asking whether the system situates a document within its original archival and historical setting rather than presenting it as free-floating text. Chronology could be tested with queries that require ordering events correctly across a span of decades or centuries. Corroboration could be tested by deliberately including contradictory sources in a test collection and observing whether the system flags the disagreement or resolves it artificially. Transparency about uncertainty could be measured by presenting queries with genuinely unresolved historical questions and checking whether the system hedges appropriately rather than manufacturing false confidence.

Benchmark Collections and a Comparative Rubric

Testing such a framework requires benchmark collections that reflect the actual diversity of archival material historians work with: personal letters and correspondence, census and vital records, digitized newspapers, military service and pension records, oral history transcripts, and photograph collections with accompanying metadata. Each of these genres carries its own provenance conventions and its own failure risks, and a system that performs well on newspapers may perform poorly on oral histories, where nuance, tone, and interviewer influence complicate straightforward retrieval.

A repeatable scoring rubric applying HAIEF criteria could then be used to compare general-purpose assistants such as ChatGPT, Claude, and Gemini against dedicated archival RAG systems purpose-built for a single institution's holdings. Such a comparison would likely show that general-purpose assistants excel at fluent synthesis but lag on provenance transparency, while dedicated archival systems, closer in spirit to the Konstantinidis pipeline, perform better on traceability but may still struggle with the interpretive reasoning that Bhatnagar's thesis identified as a persistent weakness across the board.

Recommendations for Archives Building AI-Assisted Discovery Tools

Institutions developing these tools should treat historiographical evaluation as a first-class requirement rather than an afterthought bolted on after a system already works technically. This means involving historians and archivists directly in system design, not merely as end-user testers after launch. It means building citation and provenance display into the interface itself, so that a user can see, at a glance, exactly which archival item supports each claim. It means deliberately including contradictory or ambiguous material in test collections so that a system's handling of disagreement can be assessed before deployment, rather than discovered by an unlucky researcher months later. And it means resisting the temptation to optimize purely for fluent, confident-sounding answers, since fluency and historical reliability are not the same thing and can, in the worst cases, actively work against one another.

Conclusion

RAG is not a gimmick, and the evidence gathered here, from a large-scale newspaper archive study to a humanities-focused thesis to a growing body of evaluation literature, makes clear that it represents a genuine advance over keyword search for anyone working with digitized historical material. But calling it groundbreaking requires a qualification. It is groundbreaking as a retrieval technology. It is not yet groundbreaking as a historiographical instrument, because none of the existing research has built evaluation standards around the values historians actually rely on to judge evidence. Closing that gap, through a framework like HAIEF, is not a minor refinement. It is the difference between a tool that finds documents quickly and a tool that a historian can actually trust.

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Sources:

Bhatnagar, Gauri. "Enhancing Multimodal Archival Search and Discovery in the Sound and Vision Archive Using Large Language Models and Retrieval-Augmented Generation." Master's thesis, University of Twente, August 2025. https://purl.utwente.nl/essays/108957.

Gan, Aoran. "Retrieval Augmented Generation Evaluation in the Era of Large Language Models: A Comprehensive Survey." arXiv, April 21, 2025. https://doi.org/10.48550/arXiv.2504.14891.

Jancovic, Marek. "RAG for Historians: A Radically New Way of Interacting with Historical Documents." LinkedIn, March 29, 2026. https://www.linkedin.com/pulse/rag-historians-radically-new-way-interacting-marek-jancovic-ew3xe/.

Konstantinidis, Stergios, Hayman Lotfy, Alexis Erne, Faruk Zahiragic, Min-Yen Kan, and Michalis Vlachos. "Improving Access to Historical Archives with Real-time RAG-based Systems." arXiv, July 3, 2026. https://arxiv.org/html/2607.03440v1.

Toloka. "RAG Evaluation: A Technical Guide to Measuring Retrieval-Augmented Generation." Toloka Blog, August 15, 2025. https://toloka.ai/blog/rag-evaluation-a-technical-guide-to-measuring-retrieval-augmented-generation.

Veridian Software. "What Is RAG and How Could It Support Digital Collection Search?" Veridian Software Knowledge Base, June 29, 2025. https://veridiansoftware.com/knowledge-base/a-new-way-to-search-digital-collections-introducing-rag.