Definition from ISO/CD 10303-41:1992: An SI unit is the fixed quantity used as a standard in
terms of which items are measured as defined by ISO 1000 (clause 2).
IfcSIUnit covers both standard base SI units, like meter and second, and derived SI units, like Pascal,
square meter and cubic meter.
NOTE Corresponding STEP name: SI-unit, please refer to ISO/IS 10303-41:1994
for the final definition of the formal standard.
HISTORY New entity in IFC Release 1.5.1.
|| The SI Prefix for defining decimal multiples and submultiples of the unit.
|| The word, or group of words, by which the SI unit is referred to.
The dimensional exponents of SI units are derived by function IfcDimensionsForSiUnit.