4.5.13 Spatial Structure
Spatial structures, such as site, building, storey, or spaces, may contain physical elements, including building elements, distribution elements, and furnishing elements. The containment relationship between the physical elements and the spatial structures is hierarchical, i.e. a physical element shall only be contained within a single spatial structure.
The spatial containment relationship, together with the Spatial decomposition relationship, being hierarchical as well, establishes the hiearchical project tree structure in a building information model.