<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>

• IfcSIPrefix
• ifc:Prefix
• ifc:IfcSIPrefix