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Typed host services

The engine passes a RuleContext containing the immutable project view and a type-indexed ServiceRegistry to trusted capabilities. Applications register semantic or computational services explicitly; duplicate concrete service types are rejected instead of silently replacing an implementation.

Adapter crates are peers:

  • OpenBIM implementations can provide semantic/property/relationship services.
  • Axiolid implementations can provide geometry services for IFC, proprietary CAD, or any source able to lower geometry into Axiolid.
  • ICDD implementations can provide project assembly and cross-document link services.
  • Alternate geometry backends register the same source-neutral service interfaces.

Rule packages cannot register services and cannot supply executable code. Missing required services must produce an explicit not-evaluated/backend-unavailable outcome, never a pass.

Property resolution is exposed through PropertyResolutionServiceHandle. A present response is a ResolvedProperty bound to the complete PropertyRequest, including the source-qualified object identity and property key; absence requires equivalent exact request-bound evidence. The handle rejects cross-object substitution, mismatched property keys, absent provenance, approximate values, non-finite numerics, and non-reviewable absence claims. Built-in property capabilities and property-based selectors require this service rather than treating a missing entry in an object map as proof of absence.

Relationship-based comparison candidates are exposed through RelationshipSelectionServiceHandle. A request binds the checked object, the complete selector-derived candidate universe, and either a shared-group or directional traversal query. Successful responses must stay inside that universe, use canonical unique object IDs and evidence, and prove exact completeness. Source adapters interpret native containment, hosting, and relationship structures; the engine does not read Object.relationships as authoritative source semantics.

Metric routing is exposed as MetricRoutingServiceHandle. The concrete handle wraps a backend-neutral trait object so it remains type-indexable in ServiceRegistry. Engine capabilities consume validated metric requests and bounded evidence; adapters keep native mesh and B-rep types behind the service.

Free-space area, fixed directional clearance, and constrained placement search are exposed through FreeSpaceServiceHandle. The handle enforces exact request binding and preserves asymmetric proof requirements: one obstruction or placement witness may be sufficient, while clear and no-placement verdicts require complete evidence. Placement domains distinguish unrestricted, support-grounded, and anchor-frame offset searches. Supported found witnesses require exact whole-base support evidence bound to the requested object, found frame, and maximum gap. See Free space and clearance.

Walkable-region topology is exposed through WalkabilityServiceHandle. A trusted geometry backend supplies a complete exact snapshot; engine routing distinguishes definite-width, impossible, and uncertain-width paths without importing backend cells or geometry. See Walkability topology.