IFC 4.3.0.1 (IFC4X3) development

# 5.4.3.21 IfcElementQuantity

## 5.4.3.21.1 Semantic 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.

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.

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

Base quantities are quantity definitions that are independent of a particular method of measurement and therefore internationally applicable. Base quantities are defined as gross and net values and provided by measurement of the correct geometric shape representation of the element. This specification includes a set of base quantity definition. See each subtype of IfcElement for applicable base quantities.

The following general agreements apply for each base quantity set

## 5.4.3.21.6 Formal representation

ENTITY IfcElementQuantity
SUBTYPE OF (IfcQuantitySet);
MethodOfMeasurement : OPTIONAL IfcLabel;
Quantities : SET [1:?] OF IfcPhysicalQuantity;
WHERE
UniqueQuantityNames : IfcUniqueQuantityNames(Quantities);
END_ENTITY;