Conformance levels

OSL v1 has four independent conformance levels. An engine declares which it supports via GET /osl/conformance.

Level	Covers	Who must pass it
Core	All MetricFlow pass-through + .governance, .synonyms extensions	Any OSL engine
Lance	UnstructuredFacet + JointEntity + hybrid retrieval (+ v1.2: traverse, domain-map, governed sample)	Engines supporting the unstructured plane
Lineage	OpenLineage emission with osl.semanticResolution and lance.retrieval facets	Engines integrating observability
Governance	Denormalization to policy facts for the PDP + Lance row-level ACL	Engines integrating the cell-model

Tip

Core is mandatory; Lance, Lineage and Governance are optional. A community engine may pass only Core and be valid — but an engine that doesn’t pass Lance doesn’t understand half of the OpenDome model. The OpenDome reference engine (tenant-semantic-api) passes all four.

Declaring conformance

GET /osl/conformance

{
  "engine": "opendome/tenant-semantic-api",
  "version": "<engine version>",
  "conformance": ["lance-v1", "lineage-v1"],
  "spec_url": "https://spec.opendome.eu/osl/v1/manifest.schema.json"
}

Conformance levels evolve independently of the spec version — a new level can be added without a breaking spec bump.