#### IfcElementQuantity

Natural language names

##### Semantic definitions at the entity

Entity definition

An IfcElementQuantity defines a set of derived measures of an element's physical property. Elements could be spatial structure elements (like buildings, storeys, or spaces) or building elements (like walls, slabs, finishes). The IfcElementQuantity gets assigned to the element by using the IfcRelDefinesByProperties relationship.

The optional MethodOfMeasurement attribute defines the code, e.g. from a standard method of measurement, which had been used to calculate the element quantity.

> NOTE The recognizable values for the name and the method of measurement attributes have to be agreed upon in further agreement documents, such as implementers agreements. Some of these agreements might be limited to a certain region, to which the method of measurement applies.

The name attribute, given at the individual Quantities provides a recognizable semantic meaning of the element quantity. Both information is needed to establish a precise meaning for the measure value. An optional description may be assigned to each of the Quantities. All quantities assigned by a single instance of IfcElementQuantity are deemed to have been generated according to the same method of measurement. However several instances of IfcElementQuantity are assignable to an element, thus allowing for an element having quantities generated according to several methods of measurement.

> EXAMPLE1 To exchange the net floor area of spaces in the German region (as IfcSpace), the name might be 'HNF1' (area of main function type 1), and the method of measurement might be accordingly 'DIN277' (German industry norm no. 277)

> EXAMPLE2 The same instance of IfcSpace may have a different area measure assigned in the German region according to a housing regulation, the name would be 'Wohnfläche' and the method of measurement would be '2.BV'. It would be attached to the IfcSpace by a separate IfcRelDefinesByProperties relationship.

The IfcElementQuantity can have the following subtypes of IfcPhysicalQuantity within its SET of Quantities, which count for the basis measure types used:

- count measure
- weight measure
- length measure
- area measure
- volume measure
- time measure

> HISTORY New entity in IFC Release 2x. NOTE: It replaces the calcXxx attributes used in previous IFC Releases.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
5 | MethodOfMeasurement | - |  | This attribute is out of scope for this model view definition and shall not be set. |
6 | Quantities | IfcPhysicalQuantity | S[1:?] | The individual quantities for the element, can be a set of length, area, volume, weight or count based quantities. | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | 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. | X
3 | Name | IfcLabel | [0:1] | 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
4 | Description | IfcText | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcPropertyDefinition
| 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. |
IfcPropertySetDefinition
| PropertyDefinitionOf | IfcRelDefinesByProperties @RelatingPropertyDefinition | S[0:1] | Reference to the relation to one or many objects that are characterized by the property definition. The reference may be omitted, if the property definition is used to define a style library and no instances, to which the particular style of property set is associated, exist yet. |
IfcElementQuantity
5 | MethodOfMeasurement | - |  | This attribute is out of scope for this model view definition and shall not be set. |
6 | Quantities | IfcPhysicalQuantity | S[1:?] | The individual quantities for the element, can be a set of length, area, volume, weight or count based quantities. | X

##### Formal representations

XSD Specification
`<xs:element name="IfcElementQuantity" type="ifc:IfcElementQuantity" substitutionGroup="ifc:IfcPropertySetDefinition" nillable="true"/>
<xs:complexType name="IfcElementQuantity">
<xs:complexContent>
<xs:extension base="ifc:IfcPropertySetDefinition">
<xs:sequence>
<xs:element name="Quantities">
<xs:complexType>
<xs:sequence>
<xs:element ref="ifc:IfcPhysicalQuantity" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcPhysicalQuantity"/>
<xs:attribute ref="ifc:cType" fixed="set"/>
<xs:attribute ref="ifc:arraySize" use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcElementQuantity
SUBTYPE OF (IfcPropertySetDefinition);
MethodOfMeasurement : OPTIONAL IfcStrippedOptional;
Quantities : SET [1:?] OF IfcPhysicalQuantity;
END_ENTITY;

EXPRESS-G diagram

`

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