8.11.3.3 IfcConversionBasedUnitWithOffset
8.11.3.3.1 Semantic definition
IfcConversionBasedUnitWithOffset is a unit which is converted from another unit by applying a conversion factor and an offset.
Example: The temperature unit Fahrenheit is based on the temperature unit Kelvin as follows:
$$ f = 1.8k - 459.67 $$
wherein k is an absolute temperature expressed in Kelvin and f is the same temperature in Fahrenheit. The following entity instances provide Fahrenheit as a unit:
IfcConversionBasedUnitWithOffset(
IfcDimensionalExponents(0, 0, 0, 0, 1, 0, 0),
THERMODYNAMICTEMPERATUREUNIT,
'Fahrenheit',
IfcMeasureWithUnit(
IfcThermodynamicTemperatureMeasure(1/1.8),
IfcSIUnit(THERMODYNAMICTEMPERATUREUNIT, ?, KELVIN)),
-459.67);
8.11.3.3.2 Entity inheritance
8.11.3.3.3 Attributes
| # | Attribute | Type | Description |
|---|---|---|---|
| IfcNamedUnit (2) | |||
| 1 | Dimensions | IfcDimensionalExponents |
The dimensional exponents of the SI base units by which the named unit is defined. |
| 2 | UnitType | IfcUnitEnum |
The type of the unit. |
| IfcConversionBasedUnit (3) | |||
| 3 | Name | IfcLabel |
The word, or group of words, by which the conversion based unit is referred to. |
| 4 | ConversionFactor | IfcMeasureWithUnit |
The physical quantity from which the converted unit is derived. |
| HasExternalReference | SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjects |
Reference to external information, e.g. library, classification, or document information, which is associated with the conversion-based unit. |
|
| Click to show 5 hidden inherited attributes Click to hide 5 inherited attributes | |||
| IfcConversionBasedUnitWithOffset (1) | |||
| 5 | ConversionOffset | IfcReal |
A positive or negative offset to add after the inherited ConversionFactor was applied. |
8.11.3.3.4 Examples
8.11.3.3.5 Formal representation
ENTITY IfcConversionBasedUnitWithOffset
SUBTYPE OF (IfcConversionBasedUnit);
ConversionOffset : IfcReal;
END_ENTITY;