5.1.3.20 IfcRelAggregates

RV ⓘ

AbV ⓘ

5.1.3.20.1 Semantic 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 IfcObjectDefinition.

In cases of aggregation of physical elements into a physical aggregate the shape representation of the whole (within the same representation identifier) can be taken from the sum of the shape representations of the parts.

Decompositions imply a dependency, implying that 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 relationship has to be established inside the applications.

5.1.3.20.2 Entity inheritance

- IfcRoot

5.1.3.20.3 Attributes

#	Attribute	Type	Description
IfcRoot (4)
1	GlobalId	IfcGloballyUniqueId	Assignment of a globally unique identifier within the entire software world.
2	OwnerHistory	OPTIONAL IfcOwnerHistory	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 is stored - either as addition, deletion or modification. IFC4-CHANGE The attribute has been changed to be OPTIONAL.
3	Name	OPTIONAL IfcLabel	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.
4	Description	OPTIONAL IfcText	Optional description, provided for exchanging informative comments.
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IfcRelAggregates (2)
5	RelatingObject	IfcObjectDefinition	The object definition, either an object type or an object occurrence, that represents the aggregation. It is the whole within the whole/part relationship. IFC4-CHANGE The attribute has been demoted from the supertype IfcRelDecomposes and defines the non-ordered aggregation relationship.
6	RelatedObjects	SET [1:?] OF IfcObjectDefinition	The object definitions, either object occurrences or object types, that are being aggregated. They are defined as the parts in the whole/part relationship. No order is implied between the parts. IFC4-CHANGE The attribute has been demoted from the supertype IfcRelDecomposes and defines the non-ordered set of parts within the aggregation.

Table 5.1.3.20.A

5.1.3.20.4 Formal propositions

Name	Description
NoSelfReference	The instance to with the relation points as provided by RelatingObject shall not be contained in the set of RelatedObjects.
`SIZEOF(QUERY(Temp <* RelatedObjects \| RelatingObject :=: Temp)) = 0`

Table 5.1.3.20.B

5.1.3.20.5 Concept usage

Concept	Usage	Description
IfcRoot (2)
Revision Control	General	Ownership, history, and merge state is captured using IfcOwnerHistory.
Software Identity	General	IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.
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Table 5.1.3.20.C

5.1.3.20.6 Formal representation

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