The Object Model is plane 1 of the Xema System Interface (XSI). Each object is identified by a XemaObjectRef of the shape xema://<scope-path>/<kind>/<slug>[@<version>]. The kind is drawn from the closed object-kind enum; the scope path is derived from the object's owning space, addressed by a SpaceRef — one closed vocabulary of seven tiers, which each registry narrows to an admissible subset rather than copying. Object ownership is single-writer: exactly one producing service owns each (source, kind) slice and publishes a complete projection via the xema.object-registry.projection.published.v1 CloudEvent. Consumers read refs through object-registry-api. Objects move through the lifecycle draft → published → archived; only published versions can be resolved. See the kernel package @xemahq/contracts/object.