IfcRelDefinesByType

Natural language names
Definiert durch Typ - Relation
Rel Defines By Type
Définition par type
Change log
ItemSPFXMLChangeDescription
IFC2x3 to IFC4
    IfcRelDefinesByType
      OwnerHistoryMODIFIEDInstantiation changed to OPTIONAL.
IFC4 Addendum 2
    IfcRelDefinesByType
      RelatedObjectsXMODIFIEDXsdformat changed from Default to Hidden.
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 138.

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

  1. 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.
  2. 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.
  3. 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.
instance diagram

Figure 138 — 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
#AttributeTypeCardinalityDescription G
5RelatedObjectsIfcObjectS[1:?] X
6RelatingTypeIfcTypeObject Reference to the type (or style) information for that object or set of objects.X
Inherited definitions from supertypes
Entity inheritance IfcRelDefines 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
IfcRelDefines
IfcRelDefinesByType
5RelatedObjectsIfcObjectS[1:?] X
6RelatingTypeIfcTypeObject Reference to the type (or style) information for that object or set of objects.X
Definitions applying to General Usage

Concept inheritance

#ConceptTemplateModel View
IfcRoot
IdentitySoftware IdentityGeneral Usage
Revision ControlRevision ControlGeneral Usage
Examples
Formal representations
XML 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="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;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcObject IfcTypeObject

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