Skip to content

Chapter 16 — Evidence for claims and corpora

Status: STABLE · Prerequisites: Chapter 8, Chapter 14, Chapter 15

Mental model

Retrieval plus membership, never stance. occam_claim_check returns blocks that cleared a lexical BM25 floor plus a Merkle proof that each was in the signed extraction. It does not judge whether a claim is true, false, or absent from the page in any semantic sense.

Explanation

occam_claim_check

Workflow:

  1. Live-fetch and compile the page (with playbook overlay forced to auto — no parameter to disable).
  2. Rank extracted blocks against your claim string using BM25.
  3. Return matches with Merkle proofs linking each block to the signed blockMerkleRoot.

Key fields:

Field Honest meaning
found A block cleared the lexical relevance floor
proven (only when found:false) Retrieval-complete negative: the leaf set was untruncated, so no extracted block matched. Not proof the fact is false.
verdict Always not_evaluated — claim_check does not classify support
receipt A real signed Receipt v1 over the extraction — verifiable via occam_verify
matches[].proof Merkle membership in the signed extract — not claim support

Preferred vocabulary: EVIDENCE_FOUND / NO_EVIDENCE / SUPPORTED / NOT_SUPPORTED in prose; wire proven is legacy.

Neither claim_check nor dataset_export applies a token budget — a precondition for leafSetComplete / proven:true.

occam_attest

Canonical meaning: heuristic citation assessment, not cryptographic attestation.

  • Re-runs claim-check internally; accepts claim text, not claim-check JSON.
  • Applies anchored regexes for two English shapes: X is [a] Y and X uses Y.
  • Returns supported | contradicted | related | unsupported | unknown.
  • Attaches one Merkle proof for the top block only.
  • The aggregate response is unsigned JSON.

Never describe occam_attest as attestation in the cryptographic sense.

occam_dataset_export

  • Exports a set of URLs with row metadata and a detached manifest signature.
  • Top-level ok describes export completion, not per-row success — inspect rows.
  • Manifest verification is CLI-only (occam verify --mode manifest on the host binary).

Task R step (conceptual)

Claim-check the exact sentence you plan to quote; take leaf + proof into occam_verify mode=citation; export source URLs as a dataset and verify the manifest on the CLI with --pubkey.

CHECK

NETWORK. Claim-check a sentence you know is on the page. Re-run with a paraphrase that shares no terms with the original. The second returns found:false while the page plainly states the claim — demonstrating lexical retrieval limits, not semantic absence.

LOCAL. Confirm occam_attest aggregate JSON has no signature field and cannot be passed to occam_verify.

Common misconception

"found:false with proven:true means the page does not say it." It means no extracted block cleared a lexical floor over an untruncated leaf set. Paraphrase, synonymy, non-English phrasing, text in images, content behind interaction, and anything the extractor dropped are all outside its reach.

Limitations

  • No stance evaluation in claim_check (verdict is hardcoded not_evaluated).
  • Attest understands only two English claim shapes; everything else is unknown.
  • Attest aggregate is unsigned — not verifiable as a unit.
  • Dataset manifest verify requires CLI + out-of-band PEM — not MCP-in-band.
  • Merkle proof proves block membership in the signed extract, not that the block supports your claim.
  • No truth, origin, identity, or trusted-time claims are licensed by these tools.