@actuarial-ts/interchange

The actuarial-interchange format (spec v1) for the actuarial-ts SDK: language-neutral, versioned documents that carry data, intent, results, and governance between actuarial-ts, chainladder-python, and R ChainLadder — plus the deterministic cross-implementation referee.

Install

npm install @actuarial-ts/interchange

ESM, Node >= 20. Depends on @actuarial-ts/core (>= 0.2.0 — it provides the canonicalJson/fnv1a64 this package canonicalizes and stamps with) and zod.

• Document kinds: triangle, selection, method-result, stochastic-result, study, bundle, crosscheck-report — zod schemas with inferred types, mechanically emitted to JSON Schema under schema/interchange/1.0/ (committed; a drift test fails the build if the emitted schemas and the committed files diverge).
• Canonicalization is RFC 8785 (JCS) via @actuarial-ts/core's canonicalJson; the committed cross-language vector suite (schema/interchange/1.0/jcs-vectors.json) is part of the spec.
• Integrity tags cover the semantic body only — fnv1a64(canonicalJson(<kind-named object>)) — never the envelope, so a re-export by another adapter changes the envelope, not the tag. Tags detect ACCIDENTAL divergence; they are not a security control.
• Selections travel as intent + values with a normative coherence rule: computable intents must recompute to the stated value within 1e-9 relative, verified on import (warn or refuse via a strictness flag; refusal is INCOHERENT_SELECTION). Values are authoritative only for judgmental/external intents, whose rationale is required.
• Converters: triangleToDoc/docToTriangle, selectionsToDoc/docToSelections (intent ↔ the standard averages menu), resultToDoc (chainLadder, mack, bornhuetterFerguson, benktander; Cape Cod, Clark, Munich and the stochastic layer are not yet converted and resultToDoc throws for them), and parseDocument (version-checked, integrity-verified, warning-channeled).
• The referee: crosscheck({ a, b, tolerance?, selection?, createdAt }) compares two method-result documents by appliesTo tags and convention profile, computes per-origin and total relative deviations, applies requested-vs-effective downgrades, and returns a crosscheck-report with verdict agree | disagree | not-comparable | verified-by-value. Convention profiles (deterministic-cl, mack1993-vw) are shipped as data, including each engine's pinned alignment parameters.

Version handling (spec 3.5): wrong-major documents throw ReservingError("UNSUPPORTED_VERSION"); same-major unknown minor fields are accepted and preserved (schemas are passthrough), and governance/extensions round-trip opaquely.

Everything is pure and browser-safe: no clock reads (createdAt is caller-supplied), no randomness, no node builtins. Depends on @actuarial-ts/core and zod only; zod-to-json-schema is a build-time devDependency used by npm run emit-schema (which builds first, then regenerates the committed JSON Schemas).

This package is designed to support the actuary's compliance with the ASOPs; cross-implementation agreement supports, but does not by itself constitute, the model validation contemplated by ASOP No. 56.

Two referees

crosscheck compares DERIVATIONS: two deterministic method-result documents, where any deviation beyond float noise is a real disagreement.

crosscheckStochastic compares DRAWS: two stochastic-result documents, where the expected disagreement is nonzero and set by sampling theory. Its tolerance is derived from the simulation count and the observed coefficient of variation rather than declared, so it tightens as n grows, and it withholds that allowance from two results that both claim seeded-reproducible at one seed. See docs/interop/reproducibility.md.

License

Apache-2.0. See LICENSE and NOTICE.