IfcReference

Semantic definitions at the entity

Entity definition

This entity is used to refer to a value of an attribute on an instance. It may refer to the value of a scalar attribute or a value within a collection-based attribute. Referenced attributes may be direct values, object references, collections, inverse object references, and inverse collections. References may be chained to form a path of object-attribute references.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	TypeIdentifier	IfcIdentifier	?	Optional identifier of the entity or type such as 'IfcMaterialLayerSet'. For entity, type, or select-based references within a collection, this resolves the reference to such type. If omitted, the type is assumed to be the same as the declared referencing attribute. EXAMPLE IfcRelAssociatesMaterial.RelatingMaterial may be resolved to IfcMaterialLayerSet.	X
2	AttributeIdentifier	IfcIdentifier	?	Optionally identifies a direct or inverse attribute within an entity such as 'MaterialLayers'. If TypeIdentifier is specified and refers to an entity, the attribute must exist within the referenced entity. A null value indicates a reference to the type or entity itself, such as for indicating that the type of a value must match a specified constraint.	X
3	InstanceName	IfcLabel	?	Optionally identifies an instance within a collection according to name. If the instance has an attribute called 'Name', such attribute is used for comparison; otherwise the first STRING-based attribute of the entity is used. EXAMPLE IfcRoot-based entities such as IfcPropertySet use the Name attribute; IfcRepresentation entities use the RepresentationIdentifier attribute.	X
4	ListPositions	IfcInteger	? L[1:?]	Optionally identifies an instance within a collection according to position starting at 1. For referencing single-level collections, this attribute contains a single member; for referencing multi-level collections, then this LIST attribute contains multiple members starting from the outer-most index.	X
5	InnerReference	IfcReference	?	Optional reference to an inner value for ENTITY, SELECT, SET, or LIST attributes. A path may be formed by linking IfcReference instances together. EXAMPLE A material layer thickness may be referenced using several instances: #1=IFCREFERENCE($,'IfcSlab','HasAssociations',#2); #2=IFCREFERENCE($,'IfcMaterialLayerSet','MaterialLayers',#3); #3=IFCREFERENCE('Core','IfcMaterialLayer','LayerThickness',$);	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcReference
1	TypeIdentifier	IfcIdentifier	?	Optional identifier of the entity or type such as 'IfcMaterialLayerSet'. For entity, type, or select-based references within a collection, this resolves the reference to such type. If omitted, the type is assumed to be the same as the declared referencing attribute. EXAMPLE IfcRelAssociatesMaterial.RelatingMaterial may be resolved to IfcMaterialLayerSet.	X
2	AttributeIdentifier	IfcIdentifier	?	Optionally identifies a direct or inverse attribute within an entity such as 'MaterialLayers'. If TypeIdentifier is specified and refers to an entity, the attribute must exist within the referenced entity. A null value indicates a reference to the type or entity itself, such as for indicating that the type of a value must match a specified constraint.	X
3	InstanceName	IfcLabel	?	Optionally identifies an instance within a collection according to name. If the instance has an attribute called 'Name', such attribute is used for comparison; otherwise the first STRING-based attribute of the entity is used. EXAMPLE IfcRoot-based entities such as IfcPropertySet use the Name attribute; IfcRepresentation entities use the RepresentationIdentifier attribute.	X
4	ListPositions	IfcInteger	? L[1:?]	Optionally identifies an instance within a collection according to position starting at 1. For referencing single-level collections, this attribute contains a single member; for referencing multi-level collections, then this LIST attribute contains multiple members starting from the outer-most index.	X
5	InnerReference	IfcReference	?	Optional reference to an inner value for ENTITY, SELECT, SET, or LIST attributes. A path may be formed by linking IfcReference instances together. EXAMPLE A material layer thickness may be referenced using several instances: #1=IFCREFERENCE($,'IfcSlab','HasAssociations',#2); #2=IFCREFERENCE($,'IfcMaterialLayerSet','MaterialLayers',#3); #3=IFCREFERENCE('Core','IfcMaterialLayer','LayerThickness',$);	X

Formal representations

XML Specification

 <xs:element name="IfcReference" type="ifc:IfcReference" substitutionGroup="ifc:Entity" nillable="true"/>

 <xs:complexType name="IfcReference">

  <xs:complexContent>

   <xs:extension base="ifc:Entity">

    <xs:sequence>

     <xs:element name="InnerReference" type="ifc:IfcReference" nillable="true" minOccurs="0"/>

    </xs:sequence>

    <xs:attribute name="TypeIdentifier" type="ifc:IfcIdentifier" use="optional"/>

    <xs:attribute name="AttributeIdentifier" type="ifc:IfcIdentifier" use="optional"/>

    <xs:attribute name="InstanceName" type="ifc:IfcLabel" use="optional"/>

    <xs:attribute name="ListPositions" use="optional">

     <xs:simpleType>

      <xs:restriction>

       <xs:simpleType>

        <xs:list itemType="ifc:IfcInteger"/>

       </xs:simpleType>

      </xs:restriction>

     </xs:simpleType>

    </xs:attribute>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcReference;

  TypeIdentifier : OPTIONAL IfcIdentifier;

  AttributeIdentifier : OPTIONAL IfcIdentifier;

  InstanceName : OPTIONAL IfcLabel;

  ListPositions : OPTIONAL LIST [1:?] OF IfcInteger;

  InnerReference : OPTIONAL IfcReference;

END_ENTITY;

 EXPRESS-G diagram

Item	Change	Description
IFC2x3 to IFC4 4.0.0.0
IfcReference	ADDED
IFC4 Addendum 1 4.0.1.0
IfcReference
ListPositions	MODIFIED	Type changed from INTEGER to IfcInteger.

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	Reference
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