Aggregates

Overview

Describes a whole/part relationship in which the parent object (the whole) is aggregated from a set of child objects (the parts) by aggregation.
Aggregation is a common relationship used in the IFC model and offers a great deal of flexibility that allows objects to be broken down into their constituent parts whilst retaining information about both the whole and the individual parts.

In an aggregation, the whole is referred to as the 'relating object' whilst the parts are referred to as the 'related objects'. There is always exactly one relating object and there may be one or many related objects.

The aggregation relationship is described at a high level in the IFC model as between occurrences of IfcObject. Practically, the relationship will be between instances of subtypes of IfcObject and these inherit the relationship.

To ensure that there is clarity about entities that are participating in an aggregation, reference to this functional part within the IDM will indicate parameters for the aggregation as:

fp_aggregates[relating_object, (related_objects, related_objects)]

This recognises that the list of related objects may be from a single entity or from more than one entity. If there is only one related entity, the list will contain a single item.

Results

Declares the existence of a specific aggregation relationship

Description	Entity/Pset/Functional Part	MAN	REC	OPT
Set the occurrence of the parent entity in the relationship	IfcObject <parent subtype>
Set the occurrences of the child entities in the relationship	IfcObject <child subtypes>
Assert the parent relationship	IfcRelAggregates.RelatingObject
Assert the child relationship	IfcRelAggregates.RelatedObjects

IFC Entities Required

• IfcObject