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Metric routing

Metric routing is a typed host service, not an algorithm embedded in the rule engine. MetricRoutingService may be implemented by Axiolid or another trusted geometry backend. OpenBIM may supply semantic route candidates, but it does not own geometry and no combined OpenBIM–Axiolid adapter is required.

Canonical request

A MetricRouteRequest carries:

  • source-qualified, object-grounded origin and destination points;
  • coordinates in canonical metres;
  • a validated mobility profile: radius, clear height, maximum step, and maximum slope.

NaN, infinity, and negative dimensions are rejected before backend execution. MetricRoutingServiceHandle validates that a backend response starts and ends at the requested points. The handle is a concrete type that can be registered in ServiceRegistry and consumed through RuleContext.

Bounded shortest-distance evidence

LengthInterval stores inclusive lower and upper bounds. Exact evidence has equal bounds. Policy comparison is intentionally three-valued:

  • Satisfied: the upper bound meets the maximum;
  • Violated: the lower bound exceeds the maximum;
  • Indeterminate: the interval straddles the threshold.

A known longer route plus an unavailable shortcut can therefore prove route existence, but cannot produce an exact shortest-distance verdict. Raster or tolerance-based backends may return conservative bounds rather than silently upgrading an approximation.

Negative results

MetricRouteOutcome::Blocked requires CompleteMetricEvidence: exact, reviewable provenance that topology and relevant obstacles were complete for the query. BlockedMetricRouteEvidence binds that proof to the complete request, including endpoints and mobility profile; the service handle rejects evidence returned for another request. Missing geometry, partial obstacle composition, unsupported connectors, resource limits, and backend failures return MetricRoutingError; they never become Blocked or a passing rule result.

The engine contract contains no mesh, B-rep, IFC entity, Axiolid kernel, OpenCascade, or vendor type.