The property with a single value IfcPropertySingleValue defines a property object which has a single (numeric or descriptive) value assigned. It defines a property - single value combination for which the property Name, an optional Description, and an optional NominalValue with measure type is provided. In addition, the default unit as specified within the project unit context can be overriden by assigning an Unit.
The unit is handled by the Unit attribute, see Table 1 for an example of various single value properties:
Table 1 — Single value properties with values, measure types and units
HISTORY New entity in IFC1.0.
IFC2x CHANGE Entity has been renamed from IfcSimpleProperty.
IFC2x3 CHANGE Attribute NominalValue has been made OPTIONAL with upward compatibility for file based exchange.
|HasExternalReferences||SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjects||Reference to an external reference, e.g. library, classification, or document information, that is associated to the property definition.|
> IFC4 CHANGE New inverse attribute.
|1||Name||IfcIdentifier||Name for this property. This label is the significant name string that defines the semantic meaning for the property.|
|2||Description||OPTIONAL IfcText||Informative text to explain the property.|
|PartOfPset||SET [0:?] OF IfcPropertySet FOR HasProperties||Reference to the IfcPropertySet by which the IfcProperty is referenced.|
> IFC4 CHANGE New inverse attribute to navigate from IfcProperty to IfcPropertySet with upward compatibility for file based exchange.
|PropertyForDependance||SET [0:?] OF IfcPropertyDependencyRelationship FOR DependingProperty||The property on whose value that of another property depends.|
|PropertyDependsOn||SET [0:?] OF IfcPropertyDependencyRelationship FOR DependantProperty||The relating property on which the value of the property depends.|
|PartOfComplex||SET [0:?] OF IfcComplexProperty FOR HasProperties||Reference to the IfcComplexProperty in which the IfcProperty is contained.|
> IFC4 CHANGE The cardinality has changed to 0..n to allow reuse of instances of IfcProperty in several IfcComplexProperty with upward compatibility for file based exchange.
|HasConstraints||SET [0:?] OF IfcResourceConstraintRelationship FOR RelatedResourceObjects||User-defined constraints for the property.|
|HasApprovals||SET [0:?] OF IfcResourceApprovalRelationship FOR RelatedResourceObjects||User-defined approvals for the property.|
|3||NominalValue||OPTIONAL IfcValue||Value and measure type of this property. |
> NOTE By virtue of the defined data type, that is selected from the SELECT IfcValue, the appropriate unit can be found within the IfcUnitAssignment, defined for the project if no value for the unit attribute is given.
> IFC2x3 CHANGE The attribute has been made optional with upward compatibility for file based exchange.
|4||Unit||OPTIONAL IfcUnit||Unit for the nominal value, if not given, the default value for the measure type (given by the TYPE of nominal value) is used as defined by the global unit assignment at IfcProject.|
ENTITY IfcPropertySingleValue SUBTYPE OF (IfcSimpleProperty); NominalValue : OPTIONAL IfcValue; Unit : OPTIONAL IfcUnit; END_ENTITY;