Retrieval that answers—or abstains
Check retrieved sources and decline unsupported answers.
Reviewed: 2026-10-03
Illustrated teaching example • Fictional data
Narration: Microsoft Mark · locally synthesized

00:00:00.000 — Retrieval supplies evidence, not certainty.

Retrieval can bring relevant documents into a model request. It does not guarantee the right document, current version, authorized access, or a supported answer. Begin with a simple baseline and add retrieval only when the task and corpus justify it.

Visual description:
Question → Authorized sources → Checked answer

00:00:18.875 — Inspect the evidence path.

The application retrieves permitted material, selects passages, supplies them to the model, and checks the answer. Observe the retrieved passages and identifiers. Embeddings and reranking are possible retrieval components, not requirements for every task. A small collection may work well with simpler search.

Visual description:
Question
Authorized retrieval
Selected passages
Generated answer
Support check
Compare with a simpler baseline.

00:00:42.625 — A document does not answer every question.

In this fictional example, the source says the office opens at nine on Monday and applications require human review. The visitor asks for the application deadline. Neither fact supplies a deadline. An answer naming a deadline would invent information, even if it cites the office hours document.

Visual description:
Retrieved source: Opens 09:00 Monday. Human review required.
Question: What is the application deadline?
The relevant-looking passage lacks the requested fact.

00:01:04.500 — Abstain with a useful next step.

A useful response says the supplied sources do not state a deadline. It can identify what the sources do establish, then request an authoritative deadline notice or direct the learner to verify it. This preserves usefulness without confusing retrieval relevance with answer support.

Visual description:
The supplied sources do not state an application deadline. They establish Monday opening time and human review. Obtain the authoritative deadline notice before answering.

00:01:25.125 — Check access, versions and hostile content.

Verify that the user may access each source and that the selected version applies. Retrieved content can contain instructions aimed at the system; keep it separate from legitimate permissions and developer rules. Test missing evidence, conflicting sources, stale versions, and attempted access to restricted documents.

Visual description:
Access: User authorized for the source
Version: Applicable authoritative material
Support: Passage supports this claim
Injection: Content cannot change permissions

00:01:48.167 — Evaluate answer and abstention together.

Build small fictional cases with supported answers, missing facts, and denied sources. Check the retrieved evidence and the final response. Passing requires both correct supported answers and honest abstention. High answer coverage is not useful if unsupported claims slip through.

Visual description:
Can your workflow recognize an unanswerable case?
Supported answer case.
Missing deadline case.
Unauthorized source case.
Your evidence: sources, answers, abstentions and failure checks.