IfcPropertyDefinition

BACnet MVD

#### IfcPropertyDefinition

Natural language names

| Merkmal - Definition
| Property Definition
| Définition de propriété

##### Semantic definitions at the entity

Entity definition

IfcPropertyDefinition defines the generalization of all characteristics (i.e. a grouping of individual properties), that may be assigned to objects. Currently, subtypes of IfcPropertyDefinition include property set occurrences, property set templates, and property templates.

- Property set template - IfcPropertySetTemplate, a collection of property templates that determine the definition of properties used within a project context.
- Property template - IfcPropertyTemplate, a single template that determines the definition of a particular property used in the same project context. The template may determine the name, description, data type, the unit, or a standard expression for each property that is based on that template.
- Property set occurrence - IfcPropertySet, a set of individual properties (that may or may not be determined by a property template) holding individual values, measure types and units, and are associated to an object occurrence or object type.

> NOTE The subtype hierarchy of IfcPropertyDefinition also includes statically defined property sets as IfcPreDefinedPropertySet. Those are rarely used collections of fixed attributes combined in an entity definition. The IfcPreDefinedPropertySet can not be determined by an IfcPropertySetTemplate.

> NOTE Individual properties, (subtypes of IfcProperty), are currently not included in the subtype hierarchy of IfcPropertyDefinition. This anomaly is due to upward compatibility reasons with earlier releases of this standard.

Property definitions define information that is shared among multiple instances of objects, either object occurrences or object types. IfcPropertyDefinition's (by their instantiable subtypes) can participate within the following relationships:

- Assignment to a project context - an HasContext relationship to IfcRelDeclares that establishes the project context in which this property definition is declared. This relationship is predominately applicable to subtypes of IfcPropertyTemplateDefinition.
- Association to external resources - an HasAssociation relationship to IfcRelAssociates that refers to external sources of information (most notably a classification or document) and creates a uni-directional association. There is no dependency implied by the association.

Subtypes are included in more specific relationships, see IfcPropertySetDefinition and IfcPropertyTemplateDefinition for details.

> HISTORY New entity in IFC2.0

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
| HasContext | IfcRelDeclares @RelatedDefinitions | S[0:1] |  |  | X
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | Reference to the relationship IfcRelAssociates and thus to those externally defined concepts, like classifications, documents, or library information, which are associated to the property definition. |  | 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
IfcPropertyDefinition
| HasContext | IfcRelDeclares @RelatedDefinitions | S[0:1] |  |  | X
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | Reference to the relationship IfcRelAssociates and thus to those externally defined concepts, like classifications, documents, or library information, which are associated to the property definition. |  | 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

##### Formal representations

XML Specification
`<xs:element name="IfcPropertyDefinition" type="ifc:IfcPropertyDefinition" abstract="true" substitutionGroup="ifc:IfcRoot" nillable="true"/>
<xs:complexType name="IfcPropertyDefinition" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcRoot"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcPropertyDefinition
ABSTRACT SUPERTYPE OF(ONEOF(IfcPropertySetDefinition, IfcPropertyTemplateDefinition))
SUBTYPE OF (IfcRoot);
INVERSE
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
HasAssociations : SET [0:?] OF IfcRelAssociates FOR RelatedObjects;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcDefinitionSelect

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