<xs:attribute name="PremiumType" use="optional">
    <xs:simpleType>
        <xs:restriction base="xs:NMTOKEN">
            <xs:enumeration value="premium" />
            <xs:enumeration value="sum_insured_allowance_premium" />
            <xs:enumeration value="estimated_premium" />
            <xs:enumeration value="endorsement_premium" />
            <xs:enumeration value="endorsement_return_premium" />
            <xs:enumeration value="special_acceptance_premium" />
            <xs:enumeration value="deposit_premium" />
            <xs:enumeration value="minimum_and_deposit_premium" />
            <xs:enumeration value="minimum_premium" />
            <xs:enumeration value="gnpi_estimated_subject_premium" />
            <xs:enumeration value="estimated_premium_income" />
            <xs:enumeration value="basis_of_deposit_premium" />
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>