Natural language names
Einheit - Zuweisung
Unit Assignment
Assignation d'unité
Semantic definitions at the entity
Entity definition

IfcUnitAssignment indicates a set of units which may be assigned. Within an IfcUnitAssigment each unit definition shall be unique; that is, there shall be no redundant unit definitions for the same unit type such as length unit or area unit. For currencies, there shall be only a single IfcMonetaryUnit within an IfcUnitAssignment.

NOTE  A IfcProject has a unit assignment which establishes a set of units which will be used globally within the project, if not otherwise defined. Other objects may have local unit assignments if there is a requirement for them to make use of units which do not fall within the project unit assignment.

All measures used in the geometric representation items are directly defined by the IfcUnitAssignment. The minimum set of units that shall be declared by the unit assignment has to include length unit and plane angle units if the IFC data set includes shape representations.

HISTORY  New entity in IFC1.5.1.
Attribute definitions
#AttributeTypeCardinalityDescription G
1UnitsIfcUnitS[1:?] Units to be included within a unit assignment.X
Formal Propositions
WR01Checks that the set of globally assigned units has each unit type (either of type IfcNamedUnit,IfcDerivedUnit, or IfcMonetaryUnit) defined only once.
Inherited definitions from supertypes
Entity inheritance
Attribute inheritance
1UnitsIfcUnitS[1:?] Units to be included within a unit assignment.X
Formal representations
XML Specification
 <xs:element name="IfcUnitAssignment" type="ifc:IfcUnitAssignment" substitutionGroup="ifc:Entity" nillable="true"/>
 <xs:complexType name="IfcUnitAssignment">
   <xs:extension base="ifc:Entity">
     <xs:element name="Units">
       <xs:group ref="ifc:IfcUnit" maxOccurs="unbounded"/>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcUnit"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
EXPRESS Specification
ENTITY IfcUnitAssignment;
  Units : SET [1:?] OF IfcUnit;
  WR01 : IfcCorrectUnitAssignment(Units);

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcContext

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