MeasureTrace converts metres, kilometres, and international miles without a binary floating-point step. Every result exposes its exact rational factor, explicit decimal rounding, and a canonical JSON receipt that a deliberately independent verifier recomputes.
The scope is intentionally narrow: three length units, one bounded decimal grammar, one inspectable trust path.
Python 3.12.11 is the pinned runtime. There are no third-party runtime dependencies.
python -m measuretrace convert 1 mi km --places 6
# 1 mi -> 1.609344 km
# exact: 25146/15625
# factor: 25146/15625
# rounding: ROUND_HALF_EVEN at 6 decimal places
# receipt-sha256: <digest>
python -m measuretrace convert 1 mi km --places 6 --receipt receipt.json
python -m measuretrace verify receipt.json
python -m measuretrace serve --host 127.0.0.1 --port 8000Open http://127.0.0.1:8000/ for the server-rendered interface. It uses standard-library WSGI, local CSS, no JavaScript, no cookies, and no runtime network dependency.
The registry stores metres per unit as reduced rational numbers:
| Symbol | Definition used |
|---|---|
m |
1/1 m |
km |
1000/1 m |
mi |
201168/125 m = 1609.344 m exactly |
Definitions are anchored to primary standards sources:
- BIPM: SI base unit metre
- BIPM: SI prefixes, where kilo is
10^3 - NIST: revised unit conversion factors, where the international/statute mile is
1609.344 mexactly - NIST SP 811 Appendix B.8, an independent NIST table of the same mile factors
Decimal inputs are bounded to 80 characters, 50 mantissa digits, and adjusted exponents from -100 through 100. Results remain Fraction values until the selected rounding rule is applied. Supported rules are half-even, half-up, and toward zero, at 0–12 decimal places.
The receipt schema is documented in docs/receipt-v1.schema.json. measuretrace.verifier intentionally does not import the conversion core or registry module; it owns a small duplicated trust root and recomputes the input, factor, exact result, rounded result, registry digest, and receipt digest.
Web UI ─┐
├─> bounded Decimal input ─> exact Fraction conversion ─> receipt builder
CLI ────┘ ▲ │
│ ▼
NIST/BIPM registry ─────────────> independent verifier
See docs/architecture.md for boundaries and data flow, and docs/threat-model.md for abuse cases, controls, deployment assumptions, and residual risks.
python -m pip install --require-hashes -r requirements-dev.lock
python tools/quality_gate.py
python -m unittest discover -s tests -v
python -m compileall -q -f measuretrace tests toolsCI uses Python 3.12.11, a hash-locked universal flit_core wheel, and GitHub Actions pinned to full commit SHAs. Its repository token has read-only contents permission and checkout credentials are not persisted. Wheel and source archive are each built twice under a fixed SOURCE_DATE_EPOCH; byte digests must match before a clean-environment wheel smoke test runs.
The evidence job starts this exact WSGI application on loopback, captures real Chrome renders at 390, 768, and 1440 CSS-pixel widths with tall viewports for the complete flow, executes the real CLI and verifier, derives architecture/workflow diagrams from the implemented modules, and computes a legacy-approximation drift dataset through the exact core. A manifest records every byte, dimension, source commit, browser version, and SHA-256.
Generated media is uploaded as a workflow artifact first. It is not committed or described as repository evidence until a later review verifies the manifest, image structure, visible output, and provenance. See docs/evidence.md.
The adopted bytes were generated by CI run 31289140743 for source commit b9f4e5a9, then checked through a separate stream-based audit and original-resolution visual review before this later commit added them.
- Responsive UI: 390 px, 768 px, and 1440 px
- Executed behavior: CLI transcript and animated result tour
- Trace model: architecture and conversion flow
- Regression evidence: legacy drift chart and source CSV
- Integrity and provenance: manifest and review record
The original application is preserved byte-for-byte under legacy/source/, anchored by Git blob IDs and the original main commit in legacy/baseline.json. Regression tests reproduce its observed conversion behavior and keep the original defects explicit. Frozen legacy code is excluded from the wheel and production execution.
MeasureTrace is not a calibration service, legal-metrology system, broad unit library, localization framework, benchmark, or claim of numerical superiority over established libraries. It does not sign receipts or establish who produced one; SHA-256 only makes post-issuance byte changes detectable.
No repository license has been selected for this repository. Reuse rights must not be inferred. The branch makes no ownership or authorship claim. Details are in docs/provenance.md.