8.11.6.4 IfcDimensionsForSIUnit（SI单位量纲）
8.11.6.4.1 语义定义（Semantic definition）
定义源自 ISO/CD 10303-41:1992：该函数返回给定SI单位的量纲指数。
参数定义： N : （输入）将返回其量纲指数的单位名称。
8.11.6.4.2 形式化表示（Formal representation）
FUNCTION IfcDimensionsForSIUnit
(n : IfcSIUnitName ) : IfcDimensionalExponents;
CASE n OF
METRE : RETURN (IfcDimensionalExponents
(1, 0, 0, 0, 0, 0, 0));
SQUARE_METRE : RETURN (IfcDimensionalExponents
(2, 0, 0, 0, 0, 0, 0));
CUBIC_METRE : RETURN (IfcDimensionalExponents
(3, 0, 0, 0, 0, 0, 0));
GRAM : RETURN (IfcDimensionalExponents
(0, 1, 0, 0, 0, 0, 0));
SECOND : RETURN (IfcDimensionalExponents
(0, 0, 1, 0, 0, 0, 0));
AMPERE : RETURN (IfcDimensionalExponents
(0, 0, 0, 1, 0, 0, 0));
KELVIN : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 1, 0, 0));
MOLE : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 1, 0));
CANDELA : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 0, 1));
RADIAN : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 0, 0));
STERADIAN : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 0, 0));
HERTZ : RETURN (IfcDimensionalExponents
(0, 0, -1, 0, 0, 0, 0));
NEWTON : RETURN (IfcDimensionalExponents
(1, 1, -2, 0, 0, 0, 0));
PASCAL : RETURN (IfcDimensionalExponents
(-1, 1, -2, 0, 0, 0, 0));
JOULE : RETURN (IfcDimensionalExponents
(2, 1, -2, 0, 0, 0, 0));
WATT : RETURN (IfcDimensionalExponents
(2, 1, -3, 0, 0, 0, 0));
COULOMB : RETURN (IfcDimensionalExponents
(0, 0, 1, 1, 0, 0, 0));
VOLT : RETURN (IfcDimensionalExponents
(2, 1, -3, -1, 0, 0, 0));
FARAD : RETURN (IfcDimensionalExponents
(-2, -1, 4, 2, 0, 0, 0));
OHM : RETURN (IfcDimensionalExponents
(2, 1, -3, -2, 0, 0, 0));
SIEMENS : RETURN (IfcDimensionalExponents
(-2, -1, 3, 2, 0, 0, 0));
WEBER : RETURN (IfcDimensionalExponents
(2, 1, -2, -1, 0, 0, 0));
TESLA : RETURN (IfcDimensionalExponents
(0, 1, -2, -1, 0, 0, 0));
HENRY : RETURN (IfcDimensionalExponents
(2, 1, -2, -2, 0, 0, 0));
DEGREE_CELSIUS : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 1, 0, 0));
LUMEN : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 0, 1));
LUX : RETURN (IfcDimensionalExponents
(-2, 0, 0, 0, 0, 0, 1));
BECQUEREL : RETURN (IfcDimensionalExponents
(0, 0, -1, 0, 0, 0, 0));
GRAY : RETURN (IfcDimensionalExponents
(2, 0, -2, 0, 0, 0, 0));
SIEVERT : RETURN (IfcDimensionalExponents
(2, 0, -2, 0, 0, 0, 0));
OTHERWISE : RETURN (IfcDimensionalExponents
(0, 0, 0, 0, 0, 0, 0));
END_CASE;
END_FUNCTION;