The objectified relationship, IfcRelReferencedInSpatialStructure is used to assign elements in addition to those levels of the project spatial structure, in which they are referenced, but not primarily contained. It is also used to connect a system to the relevant spatial element that it serves.

• NOTE: The primary containment relationship between an element and the spatial structure is handled by IfcRelContainedInSpatialStructure.

Any element can be referenced to zero, one or several levels of the spatial structure. Whereas the IfcRelContainedInSpatialStructure relationship is required to be hierarchical (an element can only be contained in exactly one spatial structure element), the IfcRelReferencedInSpatialStructure is not restricted to be hierarchical.

• EXAMPLE: A wall might be normally contained within a storey, and since it does not span through several stories, it is not referenced in any additional storey. However a curtain wall might span through several stories, in this case it can be contained within the ground floor, but it would be referenced by all additional stories, it spans.

Predefined spatial structure elements to which elements can be assigned are:

• site as IfcSite
• facility as IfcFacility or its subtypes IfcBridge, IfcBuilding, IfcMarineFacility, IfcRailway or IfcRoad
• part of facility as IfcFaciltityPart, or more specifically as IfcBuildingStorey or IfcSpace

The following picture shows the use of IfcRelContainedInSpatialStructure and IfcRelReferencedInSpatialStructure to assign an IfcCurtainWall to two different levels within the spatial structure. It is primarily contained within the ground floor, and additionally referenced within the first and second floor. 

changes 

• IFC4 changes: Type of the RelatingStructure attribute changed from IfcSpatialStructureElement to IfcSpatialElement.
• IFC4X3_RC1 changes: Type of the RelatedElements attribute changed from "set[1:?] of IfcProduct" to "set[1:?] of IfcSpatialReferenceSelect".