8.17.3.6 IfcQuantityLength
8.17.3.6.1 Semantic definition
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.
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. New entity in IFC2x. It replaces the calcXxx attributes used in previous IFC Releases.8.17.3.6.2 Entity inheritance
8.17.3.6.3 Attributes
| # | Attribute | Type | Description |
|---|---|---|---|
| IfcPhysicalQuantity (4) | |||
| 1 | Name | IfcLabel |
Name of the element quantity or measure. The name attribute has to be made recognizable by further agreements. |
| 2 | Description | OPTIONAL IfcText |
Further explanation that might be given to the quantity. |
| HasExternalReferences | SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjects |
Reference to an external reference, e.g. library, classification, or document information, that is associated to the quantity. New inverse attribute. |
|
| PartOfComplex | SET [0:1] OF IfcPhysicalComplexQuantity FOR HasQuantities |
Reference to a physical complex quantity in which the physical quantity may be contained. |
|
| IfcPhysicalSimpleQuantity (1) | |||
| 3 | Unit | OPTIONAL IfcNamedUnit |
Optional assignment of a unit. If no unit is given, then the global unit assignment, as established at the IfcProject, applies to the quantity measures. |
| Click to show 5 hidden inherited attributes Click to hide 5 inherited attributes | |||
| IfcQuantityLength (2) | |||
| 4 | LengthValue | IfcLengthMeasure |
Length measure value of this quantity. |
| 5 | Formula | OPTIONAL IfcLabel |
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. Attribute added to the end of the attribute list. |
8.17.3.6.4 Formal propositions
| Name | Description |
|---|---|
| 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. |
|
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8.17.3.6.5 Formal representation
ENTITY IfcQuantityLength
SUBTYPE OF (IfcPhysicalSimpleQuantity);
LengthValue : IfcLengthMeasure;
Formula : OPTIONAL IfcLabel;
WHERE
WR21 : NOT(EXISTS(SELF\IfcPhysicalSimpleQuantity.Unit)) OR
(SELF\IfcPhysicalSimpleQuantity.Unit.UnitType = IfcUnitEnum.LENGTHUNIT);
WR22 : LengthValue >= 0.;
END_ENTITY;