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Retrieval-augmented generation, or RAG, supplies retrieved external material to a generative model so it can answer using that material.

About 2 min to read · Take extra time for practice · AI-assisted learning notes · Expanded October 17, 2026

First, the key terms.

Chunk: A passage created by splitting a document for indexing.
Grounding: Connecting an answer’s claims to applicable evidence.

The idea, explained

A typical pipeline splits documents into passages, indexes them, retrieves candidates and places selected passages in the model’s context. Retrieval and generation fail in different ways: the right passage may be absent, poorly ranked or misunderstood. Citations should point to evidence that actually supports the answer. RAG can help update available information without changing model weights, but it is not automatic fact checking. Permissions and malicious instructions in retrieved content require separate controls.

STEP 1

Preserve useful context

A chunk should retain enough surrounding text to interpret its rule or claim. Splitting an exception away from the policy it qualifies can make retrieval misleading even when both pieces exist in the index.

STEP 2

Verify claim-level support

After retrieval, check whether each important statement follows from a passage. A citation attached to a paragraph does not necessarily support every sentence. Include document version and date where those affect applicability.

Follow a worked example.

A benefits assistant retrieves the current leave policy before answering an employee’s question. It must check the policy’s effective date and jurisdiction. A confidently written answer citing last year’s policy is still wrong.

Walk it through, one step at a time

A policy says refunds are available within 30 days, followed by an exception for custom items.
Retrieval returns only the first sentence. The generator says every purchase is refundable within 30 days.
The answer is unsupported for custom items. Improve chunking or retrieval, and require the answer to reflect the relevant exception.

Where people get stuck

More retrieved passages can introduce irrelevant or contradictory material rather than improve the answer.

Now try it yourself.

Pause before opening each answer. Explain your reasoning in your own words.

1. Check the core idea

Does a source link by itself prove the generated claim is supported?

Reveal the answer & reasoning

No. Inspect the linked passage, its date and its scope. A citation can be real but irrelevant to the claim.

2. Apply what you learned

Would a more fluent generator fix missing evidence?