What Is Citation Span Alignment, and Why Does It Matter for RAG Evidence?
Citation span alignment links each verifiable answer claim to the specific source words that support it, rather than merely naming a relevant document.
A home RAG answer can cite the correct appliance manual yet point to a page that mentions the model without supporting the stated voltage or exception. Alignment separates the answer into atomic claims, identifies the smallest sufficient source span, and preserves page or layout coordinates. This makes evidence inspectable and exposes partial support that document-level relevance would hide.
Alignment Joins an Atomic Claim to a Sufficient Passage
A claim span should contain one assertion that can be checked. Its evidence span must include the statement, qualifier, unit, subject, and condition needed to entail that assertion without relying on unrelated text elsewhere in the chunk.
Citation extraction is described as claim-to-source mapping rather than attaching a source link to an entire answer. The mapping allows an interface to highlight exactly which words support which generated statement. This distinction remains visible during later household testing.
The smallest span is not always one sentence. Tables may require a row plus header, pronouns may require an earlier sentence, and OCR layout may require a bounded page region rather than a plain text offset.
Relevance, Correctness, and Coverage Measure Different Things
A retrieved document can be topically relevant while neutral toward the final claim. Citation correctness asks whether the attached passage supports the claim, while coverage asks whether every factual claim has adequate evidence. The intermediate result must remain inspectable before automation follows.
Research on source attribution reports a gap between working, relevant links and factual citation accuracy. This demonstrates why URL validity and topical relevance cannot substitute for claim-level support evaluation. That boundary should be measured separately under realistic operating conditions.
Faithfulness is stricter still: a passage can support a claim even if the model generated it from memory and attached the source afterward. Alignment enables checking support but does not prove causal use of evidence.
Chunking and Generation Can Break the Span Relationship
A chunk may split a condition from its number, flatten table headers, or mix multiple versions. The generator can also combine two passages into one claim, strengthen cautious language, or attach one citation after several sentences.
A study of citation faithfulness distinguishes apparent citation correctness from faithful use of retrieved evidence. Its analysis reinforces that answer claims and source spans need explicit, fine-grained associations. The practical consequence appears when several sources compete for limited context.
The failure boundary is a claim whose required evidence is absent, contradictory, or distributed beyond the supported alignment method. The system should retrieve again, split or weaken the claim, or abstain rather than point to the closest topical text.
Audit Claims and Spans as Separate Objects
Sample answers from prose, OCR scans, tables, and conflicting document versions. Split them into atomic claims, record source version and page coordinates, highlight the minimal sufficient span, and label support, contradiction, or neutrality. This dependency should remain explicit in the final interface.
Compare the results with citation accuracy. Calculate citation precision, claim coverage, version correctness, resolvability, and human agreement; review numbers, negations, and conditions separately. The result must therefore be checked against the original evidence.
Pass only when every displayed citation opens an inspectable span that entails its linked claim. A relevant document without sufficient words counts as a citation failure, not partial success. This distinction remains visible during later household testing.
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