#### 8.7.2.4 IfcQuantityLength

| Quantité de longueur
| Mengenangabe - Länge

IfcQuantityLength is a physical quantity that defines a derived length measure to provide an element's physical property. It is normally derived from the physical properties of the element under the specific measure rules given by a method of measurement.

> EXAMPLE A rafter within a roof construction may be measured according to its length (taking a common cross section into account). The actual size of the length depends on the method of measurement used.

> HISTORY New entity in IFC2x. It replaces the calcXxx attributes used in previous IFC Releases.

XSD Specification:

<xs:element name="IfcQuantityLength" type="ifc:IfcQuantityLength" substitutionGroup="ifc:IfcPhysicalSimpleQuantity" nillable="true"/>
<xs:complexType name="IfcQuantityLength">
<xs:complexContent>
<xs:extension base="ifc:IfcPhysicalSimpleQuantity">
<xs:attribute name="LengthValue" type="ifc:IfcLengthMeasure" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcQuantityLength

| SUBTYPE OF (IfcPhysicalSimpleQuantity);

LengthValue | : | IfcLengthMeasure;
Formula | : | OPTIONAL IfcStrippedOptional;

| WHERE

WR21 | : | NOT(EXISTS(SELF\IfcPhysicalSimpleQuantity.Unit)) OR (SELF\IfcPhysicalSimpleQuantity.Unit.UnitType = IfcUnitEnum.LENGTHUNIT);
WR22 | : | LengthValue >= 0.;

END_ENTITY;

Attribute Definitions:

LengthValue | : | Length measure value of this quantity.
Formula | : | A formula by which the quantity has been calculated. It can be assigned in addition to the actual value of the quantity. Formulas could be mathematic calculations (like width x height), database links, or a combination. The formula is for informational purposes only. IFC4 CHANGE Attribute added to the end of the attribute list.

Formal Propositions:

WR21 | : | If a unit is given, the unit type shall be a length unit.
WR22 | : | A valid length quantity shall be greater than or equal to zero.

Inheritance Graph:

ENTITY IfcQuantityLength

| ENTITY IfcPhysicalQuantity

Name | : | IfcLabel;
Description | : | OPTIONAL IfcStrippedOptional;

| INVERSE

| ENTITY IfcPhysicalSimpleQuantity

Unit | : | OPTIONAL IfcStrippedOptional;

| ENTITY IfcQuantityLength

LengthValue | : | IfcLengthMeasure;
Formula | : | OPTIONAL IfcStrippedOptional;

END_ENTITY;

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