Agreement on using IfcRelConnectsElements for assigning IfcDoor / IfcWindow to building elements without IfcOpeningElements 

Based on          IFC2x3

Initiator            Official buildinSMART IFC2x3 CV2.0 certification programme

Effects              Coordination View 2.0

Date                    2013 07


The proper way to assign an IfcDoor / IfcWindow element to a building element is by using IfcRelVoidsElement -> IfcOpeningElement -> IfcRelFillsElement.

In some situations an IfcOpeningElement is not available:

    * If the subtraction within the building elements geometry is already done and a feature element can not be assigned

    * If the IFC export is used for presentation only (Presentation View, …).

In this cases with IfcRelConnectsElements it is possible to represent this relation without losing information. The IfcRelConnectsElements.RelatingElement then points to the building element, such as IfcWall, whereas the IfcRelConnectsElements.RelatedElement points to the IfcOpeningElement.

Note: The relation IfcRelConnects for IfcDoors / IfcWindows should be only used if there is no other solution and should only be used for Brep geometries.

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