ifc:IfcBSplineCurveForm

<xs:simpleType name="IfcBSplineCurveForm">
  <xs:restriction base="xs:string">
    <xs:enumeration value="polyline_form"/>
    <xs:enumeration value="circular_arc"/>
    <xs:enumeration value="elliptic_arc"/>
    <xs:enumeration value="parabolic_arc"/>
    <xs:enumeration value="hyperbolic_arc"/>
    <xs:enumeration value="unspecified"/>
  </xs:restriction>
</xs:simpleType>