# 5.1.3.41 IfcRelNests

AbRV ⓘ
RV ⓘ

## 5.1.3.41.1 Semantic definition

The nesting relationship IfcRelNests is a special type of the general composition/decomposition (or whole/part) relationship IfcRelDecomposes. The nesting relationship can be applied to all non physical subtypes of object and object types, namely processes, controls (like cost items), and resources. It can also be applied to physical subtypes of object and object types, namely elements having ports. The nesting implies an order among the nested parts.

Decompositions imply a dependency, i.e. the definition of the whole depends on the definition of the parts and the parts depend on the existence of the whole. The behaviour that is implied from the dependency has to be established inside the applications.

## 5.1.3.41.6 Formal representation

ENTITY IfcRelNests
SUBTYPE OF (IfcRelDecomposes);
RelatingObject : IfcObjectDefinition;
RelatedObjects : LIST [1:?] OF IfcObjectDefinition;
WHERE
NoSelfReference : SIZEOF(QUERY(Temp <* RelatedObjects | RelatingObject :=: Temp)) = 0;
END_ENTITY;