Framework

GRAIN The RAG Engineer

GRAIN is a retrieval loop: Gather, Rank, Assemble, Inspect, Navigate. Gather collects candidate passages. Rank orders them for the question actually asked. Assemble builds the context the model may see. Inspect checks that the cited chunk is the one used. Navigate decides the next lookup or the refusal. If you cannot point at the passage, you do not have retrieval. You have a fluent guess.

The moves
5

When to use it

Use it when a RAG demo cites the wrong paragraph with a straight face. If the team cannot open the chunk the model used, the loop is broken at Inspect.

The moves

  1. 01

    Gather

    Source selection, permissions, versioning, and the corpus contract that decides what belongs in the index.

  2. 02

    Rank

    First-stage retrieval (dense, sparse, or hybrid), then a reranker that orders candidates before assembly.

  3. 03

    Assemble

    Token budget, chunk order, deduplication, instruction layout, and citations that keep evidence usable.

  4. 04

    Inspect

    Failure traces, bad-chunk workflows, and eval suites that connect a wrong answer to a retrieval decision.

  5. 05

    Navigate

    TTL policy, re-ingest jobs, change detection, and signals that show operators how old an answer could be.

The book

Available now

The RAG Engineer

Retrieval Systems That Agents Can Actually Trust in Production

Open the book
The article The series

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Essays on this site

What is RAG? Retrieval, then generation

Terminology

Not a grain-size metaphor and not “we added a vector store.” GRAIN is the inspectable loop. RAG names the architecture. The RAG Engineer is available now in English and Dutch paperback, hardcover, and Kindle.

Citation

GRAIN (The RAG Engineer). Len P. van der Hof, Systems for the Strategic Self. https://lenvanderhof.com/frameworks/grain/

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