#### IfcRelAggregates

Natural language names

##### Semantic definitions at the entity

Entity definition

The aggregation relationship IfcRelAggregates is a special type of the general composition/decomposition (or whole/part) relationship IfcRelDecomposes. The aggregation relationship can be applied to all subtypes of object.

Some further specializations of decomposition may imply additional constraints and meanings, such as the requirement of aggregates to represent physical containment. In cases of physical containment the representation (within the same representation context) of the whole can be taken from the sum of the representations of the parts.

> EXAMPLE: A roof is the aggregation of the roof elements, such as roof slabs, rafters, purlins, etc. Within the same representation context, e.g. the detailed geometric representation, the shape representation of the roof is given by the shape representation of its 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 behavior that is implied from the dependency has to be established inside the applications.

> HISTORY: New entity in IFC Release 2x.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE: only the last modification in stored. | X
3 | Name | IfcLabel | [0:1] | Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule. | X
4 | Description | IfcText | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcRelationship
IfcRelDecomposes
5 | RelatingObject | IfcObjectDefinition | [1:1] | The object that represents the nest or aggregation. | X
6 | RelatedObjects | IfcObjectDefinition | S[1:?] | The objects being nested or aggregated. | X
IfcRelAggregates

##### Formal representations

XSD Specification
`<xs:element name="IfcRelAggregates" type="ifc:IfcRelAggregates" substitutionGroup="ifc:IfcRelDecomposes" nillable="true"/>
<xs:complexType name="IfcRelAggregates">
<xs:complexContent>
<xs:extension base="ifc:IfcRelDecomposes"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcRelAggregates
SUBTYPE OF (IfcRelDecomposes);
END_ENTITY;

EXPRESS-G diagram

`

Link to this page