Retrieval joined to generation

Retrieval-Augmented Generation

RAG is a technical architecture used inside AI applications. It is not a publishing tactic and it does not automatically make an answer correct.

Published 2026-07-22Last reviewed 2026-07-22Primary-source analysis
Definition

External memory for a generative model

Retrieval-Augmented GenerationRAG is an architecture that retrieves relevant external information and supplies it as context while a model generates a response.
The original architecture

Parametric and non-parametric memory

The original RAG paper described a system combining a pretrained sequence-to-sequence model with a dense vector index of documents. The generator used retrieved passages alongside model parameters to answer knowledge-intensive questions.

The research addressed limits in accessing and updating knowledge stored only in model parameters. It also made retrieved text human-readable and updateable through changes to the document index.

A modern RAG pipeline

More than one retrieval call

  1. Collect and govern the knowledge sources.
  2. Parse, clean and divide documents into usable passages.
  3. Index passages through lexical, vector or hybrid methods.
  4. Transform the user request into one or more retrieval queries.
  5. Retrieve and rerank candidate evidence.
  6. Assemble context within the model’s limits.
  7. Generate the response and, when supported, attach citations.
  8. Evaluate retrieval, faithfulness, safety and user outcome.
Failure modes

Retrieval can move the error rather than remove it

Source failure

The indexed document is stale, wrong, incomplete or unauthorized.

Retrieval failure

The correct evidence exists but the query or ranking selects a weaker passage.

Context failure

The passage loses an important exception or exceeds the context budget.

Generation failure

The model misreads, combines or overstates the retrieved material.

Citation failure

A link is shown even though it does not fully support the sentence.

Security failure

Prompt injection, weak permissions or exposed private content changes the behaviour.

RAG and the public web

The publisher controls evidence, not the pipeline

A website can make accurate information crawlable, structured and easy to retrieve. The website owner does not select the external product’s vector model, chunk size, reranker, context window or prompt.

This is why REG and RAG must remain separate: REG prepares identity and facts; RAG is the architecture that an AI-product team implements.

Source trail

Primary material behind this analysis

Retrieval-Augmented Generation for Knowledge-Intensive NLP Tasks

The original RAG paper combining parametric generation with retrieved non-parametric memory.

Open the original source at arXiv →

Related reading

Continue through the discovery stack

Information Retrieval Explained

A practical guide to lexical, semantic, hybrid, graph and structured retrieval, failure modes, passage design and evaluation.