The voided wall or slab (IfcRelVoidsElement.RelatingBuildingElement).
Its current coordinates, native units.
The opening placement's Location point: Offset is its x, Sill its z (native units).
Along the host's local X to the opening's placement origin, metres (the centre, for an authored one).
The opening's bottom above the host's placement origin, metres.
The IfcDoor / IfcWindow in the opening (IfcRelFillsElement); null for a bare opening.