Conversion identity
Rounding never becomes missing money
converted = half_even(source × rate) + residualThe selected rate and explicit residual are retained in lineage, so the identity can be replayed exactly.
Technical trust
A consolidation result should arrive with its path.
Exasum binds exact financial decisions to source facts, effective configuration, live authority, and historical versions, then preserves the released evidence as canonical bytes.
- Financial representation
- Exact decimal strings
- Business judgement
- Owned domain decisions
- Historical evidence
- Sealed and append-only
Evidence lineage
The explanation travels with the number
Each stage fixes the coordinates required by the next. A published result can be inspected from retained evidence instead of reconstructed from today's mutable setup.
01
Source
Sealed rows, provenance, and stable coordinates
02
Meaning
Published charts, dimensions, and mapping paths
03
Inputs
Effective rates, ownership, scope, and rules
04
Decision
Conversion, aggregation, NCI, and eliminations
05
Publication
Classified results, exceptions, and lineage
06
Release
Approved manifest and print-artifact digests
Exact arithmetic
ISO 4217 LIST ONE
165 PINNED CURRENCIES
Precision belongs to the currency, not the interface
Money and rates never pass through binary floating point. API values are decimal strings, database values are exact numerics, and each supported currency carries the precision at which money may be accepted and rounded.
| Currency | Minor unit | Accepted | Rejected |
|---|---|---|---|
| USD | 2 | "1250.45" | "1250.451" |
| JPY | 0 | "1250" | "1250.5" |
| KWD | 3 | "1250.455" | "1250.4551" |
| CLF | 4 | "1250.4550" | "1250.45501" |
Conservation
Every amount is carried or named
Split mappings conserve their source contribution. Ownership paths add exactly. Accepted elimination entries sum to zero. Out-of-tolerance differences remain discrepancies instead of disappearing into an adjustment.
Decision integrity
The strongest available mechanism owns each guarantee
Types and pure decisions carry business meaning; PostgreSQL independently defends critical storage invariants; integration evidence proves the real path reaches both.
01
One source of judgement
A deterministic financial answer from validated, owned inputs is a synchronous domain decision. HTTP and database code acquire authority and facts, then persist that owned outcome without recalculating it.
02
Immutable historical meaning
Source snapshots, charts, mappings, ownership, group scope, rates, eliminations, publications, and releases are sealed or append-only. A correction creates later evidence.
03
Independent database defence
Foreign keys, checks, row-level security, transition guards, deferred completeness contracts, and restricted database roles independently reject critical invalid states.
04
Executable evidence
Domain vectors prove decisions; real-database and router contracts prove the production path; browser journeys prove the visible workflow reaches those mechanisms.
Exact release
The approved report is a versioned document
Release pins the group, book, period, primary and comparative publications, section order and commentary, presentation policy, attachments, approval, and release attribution.
The server renders a self-contained HTML artifact, hashes it, embeds its digest and byte length in canonical newline-terminated JSON, hashes those exact manifest bytes, and verifies stored evidence on download.
{
"schema": "https://exasum.com/schemas/report-package-manifest/v2",
"package": {
"version_id": "<immutable version id>",
"group_id": "<reporting group id>",
"period": "2026-07-31",
"title": "Northstar July board package"
},
"presentation": {
"unit": "units",
"decimal_places": 2
},
"publications": [{
"role": "primary",
"consolidation_version_id": "<sealed publication id>"
}],
"artifacts": [{
"renderer_version": "report-package-print-html/1",
"sha256_digest": "<SHA-256>",
"byte_length": 28416
}],
"release": {
"approved_by": "<reviewer id>",
"released_by": "<releaser id>",
"renderer_version": "report-package-manifest/2"
}
}Independent evidence
One implementation is not one source of confidence
Ported financial rules are compared with the established OCaml behavior and independent F# scenarios. Domain vectors, database attacks, router contracts, race probes, accessibility scans, and browser journeys exercise different failure boundaries.
Domain vectors
Exact examples, properties, boundary cases, and exhaustive state transitions.
Database contracts
Real restricted-role sessions probe constraints, RLS, immutability, races, and guarded writes.
Router contracts
Production HTTP paths prove authentication, DTO strictness, transaction ordering, and exact response evidence.
Browser journeys
Keyboard, accessibility, visual, and full close-to-release scenarios exercise the customer-visible path.
This is repository evidence for an open engineering preview. It is not a certification, assurance report, production-operations claim, or service-level commitment.