IfcDerivedUnit

IfcDerivedUnit

实体定义
注：定义依据ISO/CD 10303-41:1992
派生单位是单位的表达式。
示例牛顿每平方毫米是一个推导单位。
注：对应的ISO 10303名称：derived_unit，正式标准的最终定义请参考ISO/IS 10303-41。
IFC1.5.1中的新实体。

 

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcDerivedUnit
1	Elements	IfcDerivedUnitElement	S[1:?]	The group of units and their exponents that define the derived unit.	X
2	UnitType	IfcDerivedUnitEnum	[1:1]	Name of the derived unit chosen from an enumeration of derived unit types for use in IFC models.	X
3	UserDefinedType	IfcLabel	[0:1]		X
	Dimensions :=IfcDeriveDimensionalExponents(Elements)	IfcDimensionalExponents	[1:1]	Dimensional exponents derived using the function IfcDerivedDimensionalExponents using (SELF) as the input value.	X

 

 

EXPRESS Specification

ENTITY IfcDerivedUnit;
  Elements : SET [1:?] OF IfcDerivedUnitElement;
  UnitType : IfcDerivedUnitEnum;
  UserDefinedType : OPTIONAL IfcLabel;
 DERIVE
  Dimensions : IfcDimensionalExponents := IfcDeriveDimensionalExponents(Elements);
 WHERE
  WR1 : (SIZEOF (Elements) > 1) OR ((SIZEOF (Elements) = 1) AND (Elements[1].Exponent <> 1 ));
  WR2 : (UnitType <> IfcDerivedUnitEnum.USERDEFINED) OR ((UnitType = IfcDerivedUnitEnum.USERDEFINED) AND (EXISTS(SELF.UserDefinedType)));
END_ENTITY;

 

 

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