Agreement on having the containment tree and the relative placement tree identical for spatial elements [modified 2010 for IFC2x3 CV2.0 Certification]
Based on IFC2x3
Initiator ISG Meeting-Helsinki
Effects Extended Coordination View
Date 2007 05 23
The spatial containment of IfcSpatialStructureElement forms a tree, and the local relative placement of IfcSpatialStructureElement forms another tree - both trees should be identical (i.e. if an IfcBuildingStorey is contained in #201=IFCBUILDING, then the IfcBuildingStorey.ObjectPlacement.PlacementRelTo shall point to the same instance #201=IFCBUILDING.
Added 2010 in official buildingSMART certification 2.0 program
* the uppermost spatial structure element, either an IfcSite, or an IfcBuilding, that is directly assigned to the IfcProject through Decomoses.RelatingObject, shall have no relative placement.
* the placement of the uppermost spatial structure element is provided by IfcLocalPlacement with PlacementRelTo = NIL.
Figure 1: The containment and local placement trees.