Definition from IAI: This objectified relationship, IfcRelContainedInSpatialStructure, is used to assign elements to a certain level of the spatial project structure. Any element can only be assigned once to a certain level of the spatial structure. The question, which level is relevant for which type of element, can only be answered within the context of a particular project and might vary within the various regions.

EXAMPLE A multi-storey space is contained (or belongs to) the building storey at which its ground level is, but it is referenced by all the other building storeys, in which it spans. A lift shaft might be contained by the basement, but referenced by all storeys, through which it spans. The reference relationship can be expressed by the general grouping mechanism estabished in IFC.

Predefined spatial structure elements to which elements can be assigned are

The same element can be assigned to different spatial structure elements depending on the context.

EXAMPLE A wall might be normally assigned to a storey, however the curtain wall might be assigned to the building and the retaining wall in the terrain might be assigned to the site.

HISTORY New entity in IFC Release 2x.
NOTE Previous entity IfcRelContains has been replaced.
ISSUE See issue and change log for changes made in IFC Release 2x

Use case:

 The figure shows the use of IfcRelContainedInStructure to assign a stair and two walls to two different levels within the spatial structure. 

EXPRESS specification:

ENTITY IfcRelContainedInSpatialStructure
SUBTYPE OF ( IfcRelConnects);
RelatedElements  :  SET [1:?] OF IfcElement;
RelatingStructure  :  IfcSpatialStructureElement;

Attribute definitions:

RelatedElements  :  Set of elements, which are associated with this level of the spatial structure hierarchy.
RelatingStructure  :  Spatial structure element, to which the element is associated within the spatial project structure.

References (3):

Name Type Referred through Express-G
IfcElement Entity
Attribute 'ContainedInStructure'
Diagram 1
IfcRelConnects Entity
Diagram 1
IfcSpatialStructureElement Entity
Attribute 'ContainsElements'
Diagram 1

Inheritance graph

ENTITY IfcRelContainedInSpatialStructure;
GlobalId  :  IfcGloballyUniqueId;
OwnerHistory  :  IfcOwnerHistory;
Name  :  OPTIONAL IfcLabel;
Description  :  OPTIONAL IfcText;
ENTITY IfcRelationship;
ENTITY IfcRelConnects;
ENTITY IfcRelContainedInSpatialStructure;
RelatedElements  :  SET [1:?] OF IfcElement;
RelatingStructure  :  IfcSpatialStructureElement;