IFC 4.3.x development IfcPropertySingleValue Semantic definitions at the entity

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:

  • If the Unit attribute is not given, then the unit is already implied by the type of IfcMeasureValue or IfcDerivedMeasureValue. The associated unit can be found at the IfcUnitAssignment globally defined at the project level (IfcProject.UnitsInContext).
  • If the Unit attribute is given, then the unit assigned by the Unit attribute overrides the globally assigned unit.


Name NominalValue Type (through IfcValue) Unit
Description Manufacturer "A" door IfcLabel -
PanelThickness 0.12 IfcPositiveLengthMeasure -
ThermalTransmittance 2.6 IfcThermalTransmittanceMeasure W/(m2K)

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. Attributes

# Attribute Type Description
HasExternalReferencesSET [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.
PropertyForDependanceSET [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 RelatedResourceObjectsUser-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 inheritance

dot_inheritance IfcPropertySingleValue IfcPropertySingleValue IfcSimpleProperty IfcSimpleProperty IfcPropertySingleValue->IfcSimpleProperty IfcSimpleProperty_children 5 more... IfcSimpleProperty_children->IfcSimpleProperty IfcProperty IfcProperty IfcSimpleProperty->IfcProperty IfcComplexProperty IfcComplexProperty IfcComplexProperty->IfcProperty IfcPropertyAbstraction IfcPropertyAbstraction IfcProperty->IfcPropertyAbstraction IfcPropertyAbstraction_children 3 more... IfcPropertyAbstraction_children->IfcPropertyAbstraction Formal representations

ENTITY IfcPropertySingleValue
 SUBTYPE OF (IfcSimpleProperty);
	NominalValue : OPTIONAL IfcValue;
	Unit : OPTIONAL IfcUnit;