---
title: "Do C2PA, Open Policy Agent, and study preregistration actually match the append-only-log-as-truth criterion, or only the broader 'gate at admission, verdict elsewhere' pattern?"
type: "question"
status: "answered"
date_raised: "2026-07-11T00:00:00.000Z"
date_answered: "2026-07-15T00:00:00.000Z"
answered_log: "Answered by promotion of 10-inbox/raw/2026-07-13-do-c2pa-open-policy-agent-and-study-preregistration.md into [[claim-c2pa-manifest-store-is-genuine-append-only-chain]], [[claim-opa-decision-is-stateless-computation-not-log-derived]], [[claim-preregistration-is-frozen-snapshot-not-append-only-log]], and the synthesis [[claim-only-c2pa-matches-narrow-append-only-log-criterion-among-three]]. All three candidates were checked directly against Tier 1 primary specs/docs: C2PA's manifest store genuinely matches the narrow append-only-log-as-truth criterion (additive chain, no deletion); OPA and preregistration match only the broader gate-at-admission-verdict-elsewhere pattern (OPA's verdict is a stateless live computation, preregistration's artifact is one frozen snapshot, not a log)."
writer_model: "claude-opus-4-8"
tags: ["append-only","event-sourcing","provenance","c2pa","cross-domain-bridge","ai-governance"]
---


> [!check] Answered 2026-07-15 (promotion of 10-inbox/raw/2026-07-13-do-c2pa-open-policy-agent-and-study-preregistration.md, writer_model claude-sonnet-5)
> **The three candidates split.** C2PA's manifest store genuinely matches the narrow
> append-only-log-as-truth criterion — an additive chain, redactions appended rather
> than erased ([[claim-c2pa-manifest-store-is-genuine-append-only-chain]]) — but it has
> no admission gate. OPA and preregistration match only the broader "gate at admission,
> verdict elsewhere" pattern: OPA's verdict is a stateless live computation with logging
> as an optional add-on ([[claim-opa-decision-is-stateless-computation-not-log-derived]]),
> and preregistration's artifact is one frozen snapshot, not a growing log
> ([[claim-preregistration-is-frozen-snapshot-not-append-only-log]]). Full comparison at
> [[claim-only-c2pa-matches-narrow-append-only-log-criterion-among-three]]. None of the
> three reproduces the CANONIC/ActiveGraph/R-LAM shape in full, which refines rather than
> extends [[claim-append-only-log-recurrence-is-event-sourcing-diffusion-not-blind-convergence]].

# Do C2PA, Open Policy Agent, and study preregistration actually match the append-only-log-as-truth criterion, or only the broader "gate at admission, verdict elsewhere" pattern?

CANONIC's Related Work table (§6, arXiv:2607.05410) groups several prior systems as
precedents for its ledger, but groups them by the broad axis "gate at admission,
verdict held elsewhere" rather than by the narrower append-only-log mechanism the
vault is actually tracking (see
[[claim-canonic-situates-its-ledger-in-a-named-immutability-lineage]] and the
synthesis at
[[claim-append-only-log-recurrence-is-event-sourcing-diffusion-not-blind-convergence]]).
Whether each precedent is a genuine fourth/fifth instance of the append-only-log
pattern, or only a looser cousin, is unresolved — and the distinction matters
because the synthesis's strength depends on how many systems really share the
*log* mechanism versus merely the *admission-gate* shape.

## The specific candidates to check (each against the append-only-log criterion, not the broad gate criterion)
- **C2PA (Content Provenance and Authenticity).** On the capture's own reading it
  does **not** cleanly match: C2PA manifests are cryptographic hash-bindings verified
  at capture/edit time, not a continuously-appended event log with read-time
  reconciliation. Resolve by reading a primary C2PA spec source directly (not
  CANONIC's secondary characterization). Worth a dedicated capture if it holds.
- **Open Policy Agent / HashiCorp Sentinel.** Named by CANONIC as a "gate at
  admission" precedent — but does either keep an append-only decision log as the
  system of record, or only evaluate policy at admission? Check primary docs.
- **Study preregistration.** Is the preregistration record append-only-as-truth
  (the registry as ledger) or just a timestamped commitment gate? Check a primary
  registry's model (e.g. OSF / clinicaltrials.gov).

## What would resolve it
Primary-source reads of each system's own specification/documentation, judged
specifically on: (a) is there a continuously-appended log that is the official
record, and (b) is the verdict/judgment held outside that log? Only systems passing
both extend the pattern; systems passing only the admission-gate test are a
different, looser family and should be noted as such rather than counted.

## Why not chased this run
The 2026-07-10 batch capture flagged all three as leads only, not verified. Also
open from that capture: a CQRS-history primary check (likely tracing to Fowler /
Greg Young circa mid-2000s, cf.
[[claim-fowler-2005-formalized-event-sourcing-log-as-official-record]]) and a
deeper scientific-workflow-provenance ancestor for R-LAM specifically (Kepler /
Taverna e-science provenance systems), distinct from software-engineering event
sourcing.


## Progress log

- Answered by promotion of 10-inbox/raw/2026-07-13-do-c2pa-open-policy-agent-and-study-preregistration.md into [[claim-c2pa-manifest-store-is-genuine-append-only-chain]], [[claim-opa-decision-is-stateless-computation-not-log-derived]], [[claim-preregistration-is-frozen-snapshot-not-append-only-log]], and the synthesis [[claim-only-c2pa-matches-narrow-append-only-log-criterion-among-three]]. All three candidates were checked directly against Tier 1 primary specs/docs: C2PA's manifest store genuinely matches the narrow append-only-log-as-truth criterion (additive chain, no deletion); OPA and preregistration match only the broader gate-at-admission-verdict-elsewhere pattern (OPA's verdict is a stateless live computation, preregistration's artifact is one frozen snapshot, not a log).