# 8.16.3.9 IfcPropertyEnumeration

## 8.16.3.9.1 Semantic definition

IfcPropertyEnumeration is a collection of simple or measure values that define a prescribed set of alternatives from which 'enumeration values' are selected. This enables inclusion of enumeration values in property sets. IfcPropertyEnumeration provides a name for the enumeration as well as a list of unique (numeric or descriptive) values (that may have a measure type assigned). The entity defines the list of potential enumerators to be exchanged together (or separately) with properties of type IfcPropertyEnumeratedValue that selects their actual property values from this enumeration.

The unit is handled by the Unit attribute, see Table 8.16.3.9.A for an example of a unitless property enumeration:

• If the Unit attribute is not given, than 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, the unit assigned by the unit attribute overrides the globally assigned unit.

## 8.16.3.9.5 Formal representation

ENTITY IfcPropertyEnumeration
SUBTYPE OF (IfcPropertyAbstraction);
Name : IfcLabel;
EnumerationValues : LIST [1:?] OF UNIQUE IfcValue;
Unit : OPTIONAL IfcUnit;
UNIQUE
UR1 : Name;
WHERE
WR01 : SIZEOF(QUERY(temp <* SELF.EnumerationValues |
NOT(TYPEOF(SELF.EnumerationValues[1]) = TYPEOF(temp))
)) = 0;
END_ENTITY;