Fixed contracts

Two assertions whose requirement is fixed by a named contract and decided in exact rational arithmetic.

These two assertions take no arguments. Each checks one fixed, named contract over a narrow admitted domain in exact rational arithmetic, and records the plan hash and the checker's source hash in its evidence (planHash, verifierSourceHash). A subject outside the domain refuses.

plate is the site's demo model; gauge and gapBoxes are repository fixtures: a STEP file whose declaration allows 0.95 to 1.05 mm between two parallel faces, and two 10 mm boxes 2 mm apart. Python adds rational_plate, the repository fixture rational-plate.json admitted through engine.ingest_subject; load_model reads STEP and glTF only, and no loader in geospec@beta admits a rational-plate subject. Python matchers are snake_case. A failed or refused call throws GeoSpecAssertionError in TypeScript and raises it in Python. Refusal codes add to the common refusals.

check.ts

import { readFile } from 'node:fs/promises';
import { expectGeo } from 'geospec';
import { createModelLoader } from 'geospec/model';
import { Engine } from 'geospec-engine/node';

const engine = new Engine();
const loadModel = createModelLoader({
  engine,
  readSource: async (source) => new Uint8Array(await readFile(source as string)),
});
const plate = await loadModel({ source: 'plate-with-through-bore.step', format: 'step' });
const gauge = await loadModel({
  source: 'packages/geospec-engine/native/occt/rust/tests/fixtures/parallel-plane-distance-source.step',
  format: 'step',
});
const gapBoxes = await loadModel({
  source: 'packages/geospec-engine/native/occt/rust/tests/fixtures/box-clearance/two-mm.step',
  format: 'step',
});

check.py

from pathlib import Path

from geospec import GeoSpecEngine, expect_geo, load_model

with GeoSpecEngine(model_root=".") as engine:
    plate = load_model(file="plate-with-through-bore.step", format="step")
    gauge = load_model(
        file="packages/geospec-engine/native/occt/rust/tests/fixtures/parallel-plane-distance-source.step",
        format="step",
    )
    gap_boxes = load_model(
        file="packages/geospec-engine/native/occt/rust/tests/fixtures/box-clearance/two-mm.step",
        format="step",
    )
    rational_plate = engine.ingest_subject(
        Path("packages/geospec-engine/bench/fixtures/performance-lab/rational-plate.json").read_bytes(),
        format="rational-plate", coordinate_system="z-up", source_unit="mm", output_unit="mm",
    )

toSatisfyRationalPlate

Asserts that a rational plate subject satisfies the contract geospec.plate-two-windows/v1: a 10 × 10 × 2 mm plate with two 1 mm square through-windows.

Signature

expectGeo(part).toSatisfyRationalPlate(): GeoSpecAssertion

expect_geo(part).to_satisfy_rational_plate() -> GeoSpecAssertionReport

Fields

None. The contract holds when all four predicates hold:

Predicate	Requirement
P1	The plate spans `[0, 0, 0]` to `[10, 10, 2]` exactly
P2	The material volume is exactly 196 mm³
P3	No material lies in window A, `[1.5, 1.5, 0]` to `[2.5, 2.5, 2]`
P4	No material lies in window B, `[7.5, 7.5, 0]` to `[8.5, 8.5, 2]`

Admitted geometry

Only a rational-plate subject, admitted in a z-up, millimetre frame with no resources; the Python setup above shows the call. Its source is canonical JSON with schema: 'geospec.rational-orthogonal-plate/v1', unit: 'mm', frame: 'artifact-xyz', a plate box and up to 16 windows boxes. Coordinates are reduced fractions spelt "n/d", such as "3/2".
Every window runs the plate's full height, lies strictly inside it in x and y, and is separated from every other window in x or y.
Source within 64 KiB and integers below 2⁶³; ingest_subject rejects more as a ProtocolError, before any claim.
A STEP, mesh or glTF subject refuses. The engine does not extract a plate from other geometry.

Refusal codes

GEOSPEC_UNSUPPORTED_EVIDENCE: the subject is not a rational plate, or a window breaks the layout rules.
GEOSPEC_ANALYSIS_LIMIT: the retained plate geometry exceeds the contract's fixed capacity, which no host limit raises, or the engine's maxMeshBytes.

A failed claim carries GEOSPEC_RATIONAL_PLATE_MISMATCH, listing the predicates that do not hold.

Examples

// refused (GEOSPEC_UNSUPPORTED_EVIDENCE): plate, a STEP subject is outside geospec.rational-orthogonal-plate/v1
expectGeo(plate).toSatisfyRationalPlate();

The passed case is Python only: no loader in geospec@beta admits rational_plate.

# passed: rational_plate, material volume 196/1 with both windows clear
expect_geo(rational_plate).to_satisfy_rational_plate()
# refused (GEOSPEC_UNSUPPORTED_EVIDENCE): plate, a STEP subject is outside geospec.rational-orthogonal-plate/v1
expect_geo(plate).to_satisfy_rational_plate()

toSatisfyParallelPlaneDistance

Asserts that the distance between two parallel planar faces of a STEP file lies within the limits the file itself declares.