ADR-A18: Surface-to-MORK lowering boundary

Status: Accepted Date: 2026-09-18 Supersedes: none Related: ADR-A17 (Surface unified projection authoring model), ADR-A16 (Surface projection mechanism), ADR-A19 (staged compiler architecture) Source plan: surface-mork-unified-projection-delivery-plan.md

Context

MORK is the machine-facing, provenance-rich mapping graph. It already models mork:DataMapping, mork:ShapeMapping, mork:RuleMapping, mork:QueryTemplate, and mork:ProjectionMapping, with parameter bindings, targeting specs, and provenance records. ontology/surface/docs/OUTSTANDING-ITEMS 2.md confirms mork:ProjectionMapping already exists in ontology/mork/spec/Mork.ttl and that tools/surface/mork.py lowers in both directions against it.

Authoring MORK’s mapping graph by hand — parameter bindings, targeting specs, dependency edges — is exactly the complexity ADR-A16’s Surface layer was created to spare domain authors from for Promotion and Index. Projection needs the same relief.

Decision

A srf:ProjectionContract lowers deterministically into one or more MORK mapping nodes, drawn from mork:DataMapping, mork:ShapeMapping, mork:RuleMapping, mork:QueryTemplate, and mork:ProjectionMapping as the contract’s intent requires. MORK remains the canonical mapping graph: dependency edges, parameter bindings, and provenance live there, not duplicated in Surface. Surface never emits an executable artefact (SPARQL, SHACL, SWRL, RML) directly for a Projection contract — only a validated MORK graph, which downstream compilers (ADR-A19, ADR-A23) then target.

Consequences

• A new lowering stage is required in the Surface compiler, distinct from Promotion/Index’s direct-emit path.
• Lowered output must satisfy MORK’s own completeness and validation checks before any backend compiles it — MORK validation is an acceptance gate for Surface’s Projection output, not a downstream concern.
• The namespace and toolchain assumptions recorded as unverified in ontology/surface/docs/OUTSTANDING-ITEMS 2.md §5 (the mork: prefix binding, the exact term names tools/surface/mork.py assumes) must be confirmed against ontology/mork/spec/Mork.ttl as it stands, not re-guessed, before lowering is relied on in production.
• Promotion and Index keep their existing direct-emit path; this ADR does not require routing them through MORK.