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Verify a quote against its source text via the verification ladder

Source: R/quote_provenance.R
verify_quote.Rd

Runs the verification ladder in order; the first match wins and sets verification_status accordingly. Steps:

  1. Strict offline string match (status "verified_exact", method "string_match", score 1.0)

  2. Normalized match: whitespace collapsed, smart quotes ASCII'd, NFC normalization, case-folded (status "verified_fuzzy", method "normalized_match", score 0.95)

  3. Substring search fallback: looks for normalized exact_text anywhere in the source; if found, the quote is accepted (status "verified_fuzzy", method "substring_search", score 0.85). The recorded start_char/end_char are left as-is and flagged imprecise by the lower score – the normalized-to-original offset mapping is lossy, so they are not recomputed.

  4. Embedding cosine similarity: requires provider; computes cosine between quote and source-text embeddings; matches if >= .QUOTE_EMBEDDING_VERIFICATION_THRESHOLD (status "verified_fuzzy", method "embedding_cosine", score = cosine value). Skipped silently if provider is NULL or doesn't support embeddings (the previous status sticks).

Usage

verify_quote(quote, source_text, provider = NULL)

Arguments

quote

A QuoteProvenance object from make_quote.

source_text

Character. Current source document text (re-fetched at verification time; may differ from the text used at attribution time – that's how drift is detected).

provider

Optional AIProvider. When supplied, enables the embedding-similarity step (4). When NULL, the ladder stops at step 3.

Value

The QuoteProvenance object with verification fields updated. verified_at is set to Sys.time I.

Details

Drift detection: before running the ladder, the source text is re-hashed and compared to the quote's source_text_sha256. If the hashes differ AND none of the ladder steps match, status becomes "drifted" (the corpus changed since attribution). This is distinguished from "fabricated" because it suggests the quote was real once but the source has been edited.

Failure mode: if all ladder steps fail and there is no drift, status becomes "fabricated". Caller should write the quote to the fabrication_log via log_fabrication.