IfcPropertyDependencyRelationship

BACnet MVD

#### IfcPropertyDependencyRelationship

Natural language names

| Merkmal - Abhängigkeitsrelation
| Property Dependency Relationship

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcPropertyDependencyRelationship |  |  |  |
Name | X | X | MODIFIED | Name changed from DependingProperty to Name. Type changed from IfcProperty to IfcLabel. Instantiation changed to OPTIONAL.
Description | X | X | MODIFIED | Name changed from DependantProperty to Description. Type changed from IfcProperty to IfcText. Instantiation changed to OPTIONAL.
DependingProperty | X | X | MODIFIED | Name changed from Name to DependingProperty. Type changed from IfcLabel to IfcProperty. Instantiation changed from OPTIONAL.
DependantProperty | X | X | MODIFIED | Name changed from Description to DependantProperty. Type changed from IfcText to IfcProperty. Instantiation changed from OPTIONAL.

##### Semantic definitions at the entity

Entity definition

An IfcPropertyDependencyRelationship describes an identified dependency between the value of one property and that of another.

> HISTORY New entity in IFC2x2

> IFC4 CHANGE Made subtype of IfcResourceLevelRelationship (attribute order changed).

Use Definition

Whilst the IfcPropertyDependencyRelationship may be used to describe the dependency, and it may do so in terms of the expression of how the dependency operates, it is not possible through the current IFC model for the value of the related property to be actually derived from the value of the relating property. The determination of value according to the dependency is required to be performed by an application that can then use the Expression attribute to flag the form of the dependency.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
3 | DependingProperty | IfcProperty |  | The property on which the relationship depends. |  | X
4 | DependantProperty | IfcProperty |  | The dependant property. |  | X
5 | Expression | IfcText | ? | Expression that further describes the nature of the dependency relation. |  | X

Formal Propositions

Rule | Description
--- | ---
NoSelfReference | The DependingProperty shall not point to the same instance as the DependantProperty.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcResourceLevelRelationship
1 | Name | IfcLabel | ? | A name used to identify or qualify the relationship. |  | X
2 | Description | IfcText | ? | A description that may apply additional information about the relationship. |  | X
IfcPropertyDependencyRelationship
3 | DependingProperty | IfcProperty |  | The property on which the relationship depends. |  | X
4 | DependantProperty | IfcProperty |  | The dependant property. |  | X
5 | Expression | IfcText | ? | Expression that further describes the nature of the dependency relation. |  | X

##### Formal representations

XML Specification
`<xs:element name="IfcPropertyDependencyRelationship" type="ifc:IfcPropertyDependencyRelationship" substitutionGroup="ifc:IfcResourceLevelRelationship" nillable="true"/>
<xs:complexType name="IfcPropertyDependencyRelationship">
<xs:complexContent>
<xs:extension base="ifc:IfcResourceLevelRelationship">
<xs:sequence>
<xs:element name="DependingProperty" type="ifc:IfcProperty" nillable="true"/>
<xs:element name="DependantProperty" type="ifc:IfcProperty" nillable="true"/>
</xs:sequence>
<xs:attribute name="Expression" type="ifc:IfcText" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcPropertyDependencyRelationship
SUBTYPE OF (IfcResourceLevelRelationship);
DependingProperty : IfcProperty;
DependantProperty : IfcProperty;
Expression : OPTIONAL IfcText;
WHERE
NoSelfReference : DependingProperty :<>: DependantProperty;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcProperty

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