Answer with evidence.

A citation is a place to look

A school office notice says the library closes at 17:00 on weekdays. A second current office notice says 18:00. Both can be quoted exactly. Neither quotation resolves the disagreement. Before giving a time, an assistant needs clarification from the source owner or an explicit rule establishing which notice supersedes the other.

The lab supplies fictional sources with visible publisher, freshness and fact labels. You select a proposed claim and the exact sentence that should support it. The final answer extracts only supported source text and links back to that span. This is an extractive answer: it copies the relevant text rather than generating a new explanation.

Follow a claim through separate checks

Check	Question to ask	Counterexample
Availability	Is this source and span actually in the available collection?	A removed notice cannot support the current answer
Relevance	Does this claim address the user’s requested fact?	A weekday fact does not answer a holiday question
Freshness	Does this source apply to the stated time or version?	Last term’s correct policy may be wrong this term
Publisher eligibility	Is this publisher suitable under the declared evidence policy?	An unverified discussion post is insufficient for an official schedule
Claim support	Does the selected span state the proposed fact?	The fee sentence does not establish closing time
Conflict	Does another eligible current source disagree?	Two current office notices state different times

These checks are not interchangeable. A source may be authoritative for one subject and unsuitable for another. An official publisher can still make mistakes. A fresh source can be irrelevant. A passage may precisely state something without being reliable enough to use.

The lab’s eligibility and current flags are authored scenario assumptions, not scores inferred from the text. Its exact-support rule compares explicit fact labels; it is not a general language-entailment model. An actual application needs maintained source provenance, versions, dates and a policy for disputed evidence.

Support every requested part

The library question asks for two facts: weekday closing time and whether borrowing is free. Selecting both matching spans covers 2 ÷ 2 = 100% of these declared facts. Selecting only the fee sentence covers 1 ÷ 2 = 50%, so the answer is partial. Citing the same closing-time sentence twice still covers only one fact.

This fraction measures coverage under the exercise’s rules. It is not the probability that the answer is true. More citations do not automatically mean more distinct evidence, especially if sources copied one another.

The answer panel keeps rejected proposals separate from the extracts it actually includes. Even when all requested facts have supported extracts, an additional rejected proposal remains visible in the audit. Do not report that every proposed claim was correct merely because the final filtered answer covers the question.

Handle disagreement without hiding it

Add the correct closing-time and fee claims, then introduce the conflicting office notice. The fee extract can remain; the closing-time claim becomes unresolved. The checker inspects all eligible current sources in the available collection, not only the citation you chose. This prevents selecting a convenient quotation while ignoring a known contradiction.

Absence of a conflict in this small collection is not proof that no conflict exists elsewhere. Retrieval may have missed a relevant source. Neither choosing the first result nor averaging 17:00 and 18:00 establishes the policy. A valid resolution might use a verified superseding notice, but this scenario deliberately supplies no such relationship.

Practice: what survives a conflict?

If a new notice disputes only the closing time, the fee fact remains supported by the current office fee sentence. Include that extract and explicitly state that the closing time is unresolved. If the disputed fact is the only requested fact, abstain from a factual answer until the disagreement is resolved.

Make abstention informative

The holiday question has no matching source in this collection. A weekday quotation is insufficient even if it comes from the right publisher. The answer should state that holiday hours are unavailable, not silently reuse the weekday time.

The lab distinguishes supported, partial and abstain based on the supported requested facts you have actually selected. “Abstain” with no claims selected means you have not supplied evidence; it does not prove that no source could answer. Inspect the available collection and the reported failed checks before explaining the gap.

Removing the current office notices invalidates citations to them. The archived notice and discussion post remain visible, but cannot meet the current official-policy requirement. Making a source unavailable is not the same as proving it false.

Apply the evidence policy

For guided practice, export a normal answer and compare it with the same claims under conflicting sources. Explain which checks change. For implementation practice, write tests for a valid source with an incorrect span, a removed source, a duplicate citation and an irrelevant but accurately quoted claim. Include contradictory eligible sources that the answer did not cite.

For a management decision brief, specify who maintains the source collection, which facts require human resolution, and how a partial answer should be presented. An evidence policy that always refuses may avoid some wrong answers while failing to help users; report useful supported coverage as well as rejected claims and unresolved requests.

These are public practice cases, not independently reviewed project evidence. The broader evidence-assistant project will connect retrieval, answer construction, tool boundaries and evaluation. Source support alone does not authorize an external action.