mountainash-rules-babel

Translate decision logic between formats. Babel moves mountainash-rules lattices in and out of external decision formats — CSV (with a metadata manifest sidecar) and DMN today — with validation that round trips are lossless.

Quick Start

import mountainash_rules_babel as babel

# Export a lattice (from AccumulatorEngine.build() or built by hand)
babel.export_lattice(lattice, "csv", path="rules.csv")
# -> rules.csv + rules.manifest.yaml (dimensions + aggregates)

# Re-import: the sidecar restores metadata and aggregates automatically
lattice = babel.import_lattice("rules.csv")

# DMN export (hitPolicy comes from the lattice's metadata)
babel.export_lattice(lattice, "dmn", path="rules.dmn")

# Validate a CSV round trip is lossless
report = babel.validate(lattice, checks=["round_trip"])
assert report.is_valid

Or from the command line:

babel formats                                  # list exporters/importers/validators
babel export -f dmn -i rules.csv -o rules.dmn
babel import -i rules.csv
babel validate -i rules.csv -c round_trip

The schema contract

Lattices out of AccumulatorEngine.build() are composed: each row is a combination of rules whose authoritative values live in coalesced (co_*) and aggregate (__agg_*) columns, while the plain columns are stale copies from an anchor rule. Babel's exporters normalise every lattice through a single resolver so files always carry the authoritative values under flat column names — and imports always come back flat (recombination belongs to the engine, not the file format). Don't-care values are empty cells in files and typed sentinels in frames.

The full contract — column taxonomy, sentinel encoding, sidecar manifest, DMN fail-closed rules — is documented in docs/lattice-schema.md.

Formats

Format	Import	Export	Notes
CSV	✓	✓	manifest sidecar (<stem>.manifest.yaml) restores metadata + aggregates
DMN 1.3	planned	✓	hitPolicy from metadata; UNIQUE on composed lattices fails closed unless assume_unique=True
GoRules JDM	planned	planned	optional extra: jdm
flagd / OpenFeature	planned	planned	optional extra: flagd

Validators: round_trip (real for CSV), conflicts / coverage / orphans (fail-closed until implemented — they report invalid rather than silently passing).

Installation

git clone https://github.com/mountainash-io/mountainash-rules-babel.git
cd mountainash-rules-babel
hatch env create

Requires a sibling checkout of mountainash-rules (see hatch.toml). After changing that repo, run hatch env prune here to pick up the new code.

Development

Command	Description
hatch run test:test-quick	Run tests
hatch run test:test-cov	Tests with coverage
hatch run test:test-target tests/path.py	Run specific tests
hatch run ruff:check / ruff:fix	Lint / auto-fix

See CLAUDE.md for architecture details.

Mountain Ash Ecosystem

Part of the Mountain Ash data framework ecosystem.

License

Apache License 2.0 — see LICENSE and NOTICE for details.