#### IfcRelDefines

Natural language names

##### Semantic definitions at the entity

Entity definition

A definition relationship (IfcRelDefines) that uses a type definition or property set definition (seens as partial type information) to define the properties of the object instance. It is a specific - occurrence relationship with implied dependencies (as the occurrence properties depend on the specific properties).

The IfcRelDefines relationship establishes the link between one type (specific) information and several objects (occurrences). Those occurrences then share the same type (or partial type) information.

> EXAMPLE: Several instances of windows within the IFC project model may be of the same (catalogue or manufacturer) type. Thereby they share the same properties. This relationship is established by a subtype of the IfcRelDefines relationship assigning an IfcProductType (or subtype thereof) to the IfcWindow.

> HISTORY: New entity in IFC Release 2x.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
5 | RelatedObjects | IfcObject | S[1:?] | Reference to the objects (or single object) to which the property definition applies. | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | 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. | X
3 | Name | IfcLabel | [0:1] | 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 | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcRelationship
IfcRelDefines
5 | RelatedObjects | IfcObject | S[1:?] | Reference to the objects (or single object) to which the property definition applies. | X

##### Formal representations

XSD Specification
`<xs:element name="IfcRelDefines" type="ifc:IfcRelDefines" abstract="true" substitutionGroup="ifc:IfcRelationship" nillable="true"/>
<xs:complexType name="IfcRelDefines" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcRelationship">
<xs:sequence>
<xs:element name="RelatedObjects">
<xs:complexType>
<xs:sequence>
<xs:element ref="ifc:IfcObject" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcObject"/>
<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 IfcRelDefines
ABSTRACT SUPERTYPE OF(IfcRelDefinesByProperties)
SUBTYPE OF (IfcRelationship);
RelatedObjects : SET [1:?] OF IfcObject;
END_ENTITY;

EXPRESS-G diagram

`

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