A single crosswalk entry translating one field in one connected system's native schema into the canonical model — SAP's `KUNNR` and a legacy system's `PolicyholderID` both map to the canonical entity's identifier field.
Low hundreds to low thousands per tenant, depending on connected-system count and schema depth
Versioned; a changed mapping is superseded, not overwritten, so historical requests remain explainable against the mapping that was actually in effect
Only the control-bearing entities were modelled for lifecycle. Defensible as a starting point, but it does leave the entity model uneven, and this is incompleteness rather than a finding.