IfcRelDefinesByType

BACnet MVD

#### IfcRelDefinesByType

Natural language names

| Definiert durch Typ - Relation
| Rel Defines By Type
| Définition par type

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcRelDefinesByType |  |  |  |
OwnerHistory |  |  | MODIFIED | Instantiation changed to OPTIONAL.
IFC4 Addendum 2
IfcRelDefinesByType |  |  |  |
RelatedObjects |  | X | MODIFIED | Xsdformat 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 155.

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.

Figure 155 — 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 |  | 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 |  | Assignment of a globally unique identifier within the entire software world. | X | X

2

OwnerHistory

IfcOwnerHistory

?

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

X

3 | Name | IfcLabel | ? | 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 | X
4 | Description | IfcText | ? | Optional description, provided for exchanging informative comments. |  | X
IfcRelationship
IfcRelDefines
IfcRelDefinesByType
5 | RelatedObjects | IfcObject | S[1:?] |  |  | X
6 | RelatingType | IfcTypeObject |  | Reference to the type (or style) information for that object or set of objects. |  | X

##### Definitions applying to Design Transfer View

Concept inheritance

# | Concept | Template | Model View
--- | --- | --- | ---
IfcRoot
| Revision Control | Revision Control | Design Transfer View

##### Definitions applying to BACnet View

Concept inheritance

# | Concept | Template | Model View
--- | --- | --- | ---
IfcRoot
| Revision Control | Revision Control | Design Transfer View

##### Examples

- Air terminal element

##### 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;

EXPRESS-G diagram

`

References: IfcObject IfcTypeObject

Link to this page