# IFC Model Tree Heirarchies for Buildings

**URL:** <https://forums.buildingsmart.org/t/ifc-model-tree-heirarchies-for-buildings/4759>\
**Category:** IFC\
**Tags:** ifc2x3\
**Created:** [May 18, 2023, 7:09pm UTC](https://forums.buildingsmart.org/t/ifc-model-tree-heirarchies-for-buildings/4759 "2023-05-18T19:09:52Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cgee](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/cgee/32/2091_2.png) [@cgee](https://forums.buildingsmart.org/u/cgee)\
**Post date:** [May 18, 2023, 7:09pm UTC](https://forums.buildingsmart.org/t/ifc-model-tree-heirarchies-for-buildings/4759/1 "2023-05-18T19:09:52Z")

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Where can I find examples of acceptable IFC heirarchical relationships below IfcBuildingStorey?

For example:

1. Where does Ifc Zone sit in relation to IfcSpace and IfcBuildingStorey?
2. Can there be sub entities below the main building element entities, e.g. IfcWall

Where do I find good examples sample files?

Many thanks

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**Author:** ![stefkeB](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/stefkeb/32/1755_2.png) [@stefkeB](https://forums.buildingsmart.org/u/stefkeB)\
**Post date:** [May 30, 2023, 7:32am UTC](https://forums.buildingsmart.org/t/ifc-model-tree-heirarchies-for-buildings/4759/2 "2023-05-30T07:32:29Z")

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Please don’t ask the same question multiple times in the forum.

The “Spatial Composition” concept is documented:

[https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/concepts/Object\_Composition/Aggregation/Spatial\_Composition/content.html](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/concepts/Object_Composition/Aggregation/Spatial_Composition/content.html)

The aggregation of e.g. a project, site, building, building storey… can be considered one of the possible hierarchies. The IFC schema is represented as a graph of linked entities, but most viewers display the Spatial Hierarchy as a tree, because it is a very good representation of the spatial relations.

As already answered, IfcZone is a parallel grouping, which is not strictly part of the Spatial Hierarchy. Some viewers show grouping as an alternative hierarchy, which would show also Systems (another form of grouping).

Within your second question, yes, there may be items below IfcWall, when there are e.g. Building Element Parts.

[https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcBuildingElementPart.htm](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcBuildingElementPart.htm)

Such relations are “modelled” in the schema using separate entities to represent relationships (“objectified relations”).

[https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcRelationship.htm](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcRelationship.htm)