IfcRelAggregates

Natural language names
Teil zu Ganzes Beziehung ungeordnet - Relation
Rel Aggregates
Regroupement
Change log
ItemSPFXMLChangeDescription
IFC2x3 to IFC4
    IfcRelAggregates
      OwnerHistoryMODIFIEDInstantiation changed to OPTIONAL.
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
#AttributeTypeCardinalityDescription G
5RelatingObjectIfcObjectDefinition 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
6RelatedObjectsIfcObjectDefinitionS[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
RuleDescription
NoSelfReferenceThe 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 IfcRelDecomposes IfcRelationship IfcRoot
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRoot
1GlobalIdIfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world. X
2OwnerHistoryIfcOwnerHistory? 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
3NameIfcLabel? 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
4DescriptionIfcText? Optional description, provided for exchanging informative comments.X
IfcRelationship
IfcRelDecomposes
IfcRelAggregates
5RelatingObjectIfcObjectDefinition 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
6RelatedObjectsIfcObjectDefinitionS[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
Definitions applying to General Usage

Concept inheritance

#ConceptTemplateModel View
IfcRoot
IdentitySoftware IdentityGeneral Usage
Revision ControlRevision ControlGeneral 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;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcObjectDefinition

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