SDK reference

Two facades over the same idea: your application opens a pinned canon, sends facts with a closed question, and reads back a computed answer with its grounds. The engine runs locally in WebAssembly; after install, nothing on this page needs the network except the calls that say so.

Start here if you are new:

• Quickstart asks one question end to end in ten minutes, in TypeScript and in Python.
• The deadline app builds the same canon into a small working application with a form, an API, and a command line.

The two facades

Output

TypeScript   npm i @arxo/law @arxo/canon-bgb-fristen
Python       pip install arxo arxo-canon-bgb-fristen

Both open de.bgb.fristen@0.1.0 — the canon of the German Civil Code provisions on periods — ask frist_ende, and read the same fields: evaluationStatus, truthStatus, value, proof, sources, hashes, issues, document. The section map below says where each piece is documented; the compatibility chapter pins every version.

One case through both facades

Every chapter reuses the quickstart case so the calls stay comparable: an event on 6 March 2026 starts a period of 14 calendar days, and the question is whether the period ends on 20 March 2026. The legal time is 17 September 2026, the time zone is Europe/Berlin, and the counting policy is the canon’s own BGB_FRISTEN_TAG.

JavaScript

import { open } from '@arxo/law';

const fristen = await open('de.bgb.fristen@0.1.0');
const r = await fristen.truth('frist_ende', ['frist', '2026-03-20'], {
  legalTime: '2026-09-17',
  timezone: 'Europe/Berlin',
  deadlinePolicy: 'urn:de:corpus:clir:bgb-fristen#BGB_FRISTEN_TAG',
  answers: [
    { predicate: 'frist_ereignis', args: ['frist', '2026-03-06'] },
    { predicate: 'frist_dauer_tage', args: ['frist', '14 calendar_day'] },
  ],
});
// r.evaluationStatus === 'COMPUTED', r.truthStatus === 'TRUE_ONLY'

Python

from arxo import open

fristen = open("de.bgb.fristen@0.1.0")
r = fristen.truth("frist_ende", ["frist", "2026-03-20"], {
    "legalTime": "2026-09-17",
    "timezone": "Europe/Berlin",
    "deadlinePolicy": "urn:de:corpus:clir:bgb-fristen#BGB_FRISTEN_TAG",
    "answers": [
        {"predicate": "frist_ereignis", "args": ["frist", "2026-03-06"]},
        {"predicate": "frist_dauer_tage", "args": ["frist", "14 calendar_day"]},
    ],
})
# r.evaluationStatus == "COMPUTED", r.truthStatus == "TRUE_ONLY"

Section map

Page	What it answers
TypeScript	Install, entry points, open overloads, the LawPackage lifecycle from open to archive, error classes
Python	Install, the real API with its snake_case aliases, the operations Python does not ship and their workaround
Loading and pinning	Why the spec is always name@version, the installed-canon hash check, lock files, checkout trees, offline mode
Facts and context	The Fact shape, how a bare value is wrapped by its declared type, every CaseInput field, what legalTime must be
Query types	When to use truth, focused_truth, why_not, collect, deadline, calc, positions, unfold, questions
Results and errors	Every evaluationStatus, the four truthStatus values, value shapes, local versus host answers, the error table
Compatibility	Version, capability, environment, and network matrices, each cell with its source

How to use this reference

Each chapter follows the same compact shape: the contract in one paragraph, the quoted signatures, the types and errors involved, the limits, and one short example over the shared frist scenario. Read the two facade chapters for the surface you code against, then the loading chapter for reproducibility, then facts and queries for the call shape, then results for the answer shape. Compatibility stays open beside your editor while versions move.

The facades are thin by design: they transport your facts to the engine and project the answer’s fields back. They never fill in a missing fact, never default a type, and never guess a policy. When a call needs something you did not supply, the answer names it — a status, a blocker, a missing input — and the chapters on queries and results show how your code turns each one into the next question.

Where the signatures come from

Signatures on these pages are quoted from the shipped declarations. The TypeScript declarations live in the facade package, the Python signatures in the facade modules:

Output

@arxo/law            canonical declarations of open, LawPackage, Answer, Fact, CaseInput
@arxo/law-client     error classes shared by both facades
arxo                 open, LawPackage, Answer, and errors in Python
@arxo/canon-bgb-fristen   the canon build: linked world, calendar, lock file, manifest

Hashes and versions on these pages are published ones. Where an operation exists in only one facade, the page says so and names the workaround.

When a version moves, start from the compatibility chapter: it maps every claim on these pages to the manifest field or declaration block it came from, so the update is a checklist instead of a search.