<xs:attribute name="gender" use="optional">
    <xs:annotation>
        <xs:documentation>One specific gender or mixed.</xs:documentation>
    </xs:annotation>
    <xs:simpleType>
        <xs:annotation>
            <xs:documentation>One specific gender or mixed.</xs:documentation>
        </xs:annotation>
        <xs:restriction id="genderQual" base="xs:string">
            <xs:enumeration id="genderQualMale" value="male" />
            <xs:enumeration id="genderQualFemale" value="female" />
            <xs:enumeration id="genderQualMixed" value="mixed" />
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>