#### 8.10.2.2 IfcSurfaceSide

IfcSurfaceSide is a denotion of whether negative, positive or both sides of a surface are being referenced.

> NOTE Definition according to ISO/CD 10303-46:1992
> - POSITIVE: The side of a surface which is in the same direction as the surface normal derived from the mathematical definition.
> - NEGATIVE: The side of a surface which is in the opposite direction than the surface normal derived from the mathematical definition.
> - BOTH: Both, positive and negative side.

> NOTE Type adapted from surface_side defined in ISO10303-46.

> HISTORY New enumeration type in IFC2.0

XSD Specification:

<xs:simpleType name="IfcSurfaceSide">
<xs:restriction base="xs:string">
<xs:enumeration value="positive"/>
<xs:enumeration value="negative"/>
<xs:enumeration value="both"/>
</xs:restriction>
</xs:simpleType>

EXPRESS Specification:

TYPE IfcSurfaceSide = ENUMERATION OF (
| POSITIVE, NEGATIVE, BOTH);
END_TYPE;

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