Agreement to disallow duplication of Property Set Names within a single object or object type
Based on IFC2x3
Initiator Official buildinSMART IFC2x3 CV2.0 certification programme
Effects Coordination View 2.0
Date 2013 09
There should be no ambiguity in assigning properties to objects. There is a built-in rule in IFC2x3 to disallow having two properties with the same Name attribute value. But there is no built-in rule to disallow having two property sets assigned to the same object having the same Name attribute values.
Therefore it is agreed:
* for each subtype of IfcObject there shall not be two or more property sets with the same Name attribute value assigned.
* for each subtype of IfcTypeObject there shall not be two or more property sets with the same Name attribute value assigned.
It is allowed to have an IfcObject with a property set name "A", and a link to an IfcTypeObject with a property set name "A" as well. In this case any property within the object assigned property set (name "A1") overrides the property (name "A1") within the type assigned property set.
IFC4 provides an explanation and example for the override of properties, that applies already to IFC2x3 as well - https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifcreldefinesbytype.htm