IfcRelAggregates

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 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.

EXAMPLE A roof is the aggregation of the roof elements, such as roof slabs, rafters, purlins, etc. Within the same representation identifier (such as the body geometric representation), the shape representation of the roof is given by the shape representation of its 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.

HISTORY New entity in IFC2x.

IFC4 CHANGE The attributes RelatingObject and RelatedObjects are demoted from the supertype IfcRelDecomposes.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
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.	X
6	RelatedObjects	IfcObjectDefinition	S[1:?]	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.	X

Formal Propositions

Rule	Description
NoSelfReference	The instance to with the relation points as provided by RelatingObject shall not be contained in the set of RelatedObjects.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRoot
1	GlobalId	IfcGloballyUniqueId		Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	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 in stored - either as addition, deletion or modification. IFC4 CHANGE The attribute has been changed to be OPTIONAL.	X
3	Name	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.	X
4	Description	IfcText	?	Optional description, provided for exchanging informative comments.	X
IfcRelationship
IfcRelDecomposes
IfcRelAggregates
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.	X
6	RelatedObjects	IfcObjectDefinition	S[1:?]	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.	X

#	Concept	Template	Model View
IfcRoot
	Identity	Software Identity	General Usage
	Revision Control	Revision Control	General Usage

Formal representations

XML 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:sequence>

     <xs:element name="RelatedObjects">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcObjectDefinition" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcObjectDefinition"/>

       <xs:attribute ref="ifc:cType" fixed="set"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRelAggregates

 SUBTYPE OF (IfcRelDecomposes);

  RelatingObject : IfcObjectDefinition;

  RelatedObjects : SET [1:?] OF IfcObjectDefinition;

 WHERE

  NoSelfReference : SIZEOF(QUERY(Temp <* RelatedObjects | RelatingObject :=: Temp)) = 0;
END_ENTITY;

 EXPRESS-G diagram

Item	Change	Description
IFC2x3 to IFC4
IfcRelAggregates
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.

	Teil zu Ganzes Beziehung ungeordnet - Relation
	Rel Aggregates
	Regroupement

IfcRelAggregates

Semantic definitions at the entity

Inherited definitions from supertypes

Definitions applying to General Usage

Formal representations