IfcRelDefinesByType

Semantic definitions at the entity

Entity definition

The objectified relationship IfcRelDefinesByType defines the relationship between an object type and object occurrences. The IfcRelDefinesByType is a 1-to-N relationship, as it allows for the assignment of one type information to a single or to many objects. Those objects then share the same object type, and the property sets and properties assigned to the object type.

The IfcRelDefinesByType links the object type definition with the object occurrence. Both may define properties by assigning an IfcPropertySet, including one or many subtypes of IfcProperty to either the object type or object occurrence, as shown in Figure 154.

There are several scenarios to define the same property set on the object type definition and object occurrence side:

All properties for all object occurrences of a common object type have the same value - then only the object type definition has a property set assigned.
All properties for all object occurrences are different, that is there are no common property values for the object type definition - then each of the object occurrence has a property set assigned.
Some properties within the same property set have common values and are assigned to the object type definition and some are occurrence specific and assigned (with potentially different values) to the object occurrences - then:
- The sum of all properties within a given property set applicable to an object occurrence is the union of properties assigned to the object type definition plus the properties assigned to the object occurrence.
- If the object occurrence has a property with the same IfcProperty.Name in an IfcPropertySet, as the corresponding object type definition, then the occurrence property value overrides the type property value.

Figure 154 — Type definition relationships

The following table provides an example of assigning

properties assigned to IfcWall	properties assigned to IfcWallType	resulting property value for individual wall
Pset_WallCommon	Pset_WallCommon
- ExtendToStructure = TRUE		TRUE
	- ThermalTransmittance = 0.375	0.375
- ExtendToStructure = FALSE	- ExtendToStructure = TRUE	FALSE

HISTORY New entity in IFC2x.

IFC4 CHANGE The attribute RelatedObjects had been demoted from the supertype IfcRelDefines to IfcRelDefinesByType.

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
5	RelatedObjects	IfcObject	S[1:?]		X
6	RelatingType	IfcTypeObject	[1:1]	Reference to the type (or style) information for that object or set of objects.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	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 - either as addition, deletion or modification.	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
IfcRelDefinesByType
5	RelatedObjects	IfcObject	S[1:?]		X
6	RelatingType	IfcTypeObject	[1:1]	Reference to the type (or style) information for that object or set of objects.	X

Definitions applying to Bridge View

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Bridge View
	User Identity	Bridge View
	Object Ownership	Bridge View

Formal representations

XSD Specification

 <xs:element name="IfcRelDefinesByType" type="ifc:IfcRelDefinesByType" substitutionGroup="ifc:IfcRelDefines" nillable="true"/>

 <xs:complexType name="IfcRelDefinesByType">

  <xs:complexContent>

   <xs:extension base="ifc:IfcRelDefines">

    <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:element name="RelatingType" type="ifc:IfcTypeObject" nillable="true"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRelDefinesByType

 SUBTYPE OF (IfcRelDefines);

  RelatedObjects : SET [1:?] OF IfcObject;

  RelatingType : IfcTypeObject;

END_ENTITY;

 EXPRESS-G diagram

Link to this page

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

	Definiert durch Typ - Relation: Relation zwischen einem Objekt und dessen Typ
	Rel Defines By Type
	Définition par type