<group name="scale">
    <choice>
        <sequence>
            <element ref="gml:unitOfMeasure">
                <annotation>
                    <documentation>Use this element to indicate an unit of measure for numeric values on
a ratio scale.</documentation>
                </annotation>
            </element>
            <element name="frame" type="gml:ReferenceType" minOccurs="0">
                <annotation>
                    <documentation>Use this element to indicate the description of a reference system for
numeric values on an interval scale.</documentation>
                </annotation>
            </element>
        </sequence>
        <element name="frame" type="gml:ReferenceType">
            <annotation>
                <documentation>Use this element to indicate the description of a reference system for
numeric values on an interval scale.</documentation>
            </annotation>
        </element>
        <element name="classification" type="gml:StringOrRefType">
            <annotation>
                <documentation>Use this element to indicate an informally or externally described
classification scheme for values on an Ordinal or Nominal scale.</documentation>
            </annotation>
        </element>
        <element name="noScale" type="boolean" fixed="true" />
    </choice>
</group>