#### 8.5.2.10 IfcSIPrefix

> NOTE Definition according to ISO/CD 10303-41:1992
> An SI prefix is the name of a prefix that may be associated with an SI unit. The definitions of SI prefixes are specified in ISO 1000 (clause 3).

> NOTE The prefix defines multiples and submultiples of the SI units.

> NOTE Type adapted from si_prefix defined in ISO 10303-41.

Enumerated Item Definitions:

- EXA: 10^18.
- PETA: 10^15.
- TERA: 10^12.
- GIGA: 10^9.
- MEGA: 10^6.
- KILO: 10^3.
- HECTO: 10^2.
- DECA: 10.
- DECI: 10^-1.
- CENTI: 10^-2.
- MILLI: 10^-3.
- MICRO: 10^-6.
- NANO: 10^-9.
- PICO: 10^-12.
- FEMTO: 10^-15.
- ATTO: 10^-18.

> HISTORY New entity in IFC1.5.1.

XSD Specification:

<xs:simpleType name="IfcSIPrefix">
<xs:restriction base="xs:string">
<xs:enumeration value="exa"/>
<xs:enumeration value="peta"/>
<xs:enumeration value="tera"/>
<xs:enumeration value="giga"/>
<xs:enumeration value="mega"/>
<xs:enumeration value="kilo"/>
<xs:enumeration value="hecto"/>
<xs:enumeration value="deca"/>
<xs:enumeration value="deci"/>
<xs:enumeration value="centi"/>
<xs:enumeration value="milli"/>
<xs:enumeration value="micro"/>
<xs:enumeration value="nano"/>
<xs:enumeration value="pico"/>
<xs:enumeration value="femto"/>
<xs:enumeration value="atto"/>
</xs:restriction>
</xs:simpleType>

EXPRESS Specification:

TYPE IfcSIPrefix = ENUMERATION OF (
| EXA, PETA, TERA, GIGA, MEGA, KILO, HECTO, DECA, DECI, CENTI, MILLI, MICRO, NANO, PICO, FEMTO, ATTO);
END_TYPE;

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