<xs:attributeGroup name="BookingClassPrefGroup">
    <xs:annotation>
        <xs:documentation xml:lang="en">Booking class code and preference level for specifying booking classes preferred/not preferred in a request.</xs:documentation>
    </xs:annotation>
    <xs:attribute name="ResBookDesigCode" type="UpperCaseAlphaLength1to2" use="required">
        <xs:annotation>
            <xs:documentation xml:lang="en">Booking class code</xs:documentation>
        </xs:annotation>
    </xs:attribute>
    <xs:attributeGroup ref="PreferLevelGroup">
        <xs:annotation>
            <xs:documentation xml:lang="en">The preference level for the booking class.</xs:documentation>
        </xs:annotation>
    </xs:attributeGroup>
    <xs:attribute name="ResBookDesigCodeType" use="optional">
        <xs:annotation>
            <xs:documentation xml:lang="en">To specify the types of RBD's (Res Book Desig Codes) that should be returned as opposed to a specific RBD.</xs:documentation>
        </xs:annotation>
        <xs:simpleType>
            <xs:restriction base="xs:NMTOKEN">
                <xs:enumeration value="Displayable">
                    <xs:annotation>
                        <xs:documentation xml:lang="en">Only return displayable RBDs.</xs:documentation>
                    </xs:annotation>
                </xs:enumeration>
                <xs:enumeration value="NonDisplayable">
                    <xs:annotation>
                        <xs:documentation xml:lang="en">Only return non-displayable RBD's.</xs:documentation>
                    </xs:annotation>
                </xs:enumeration>
                <xs:enumeration value="All">
                    <xs:annotation>
                        <xs:documentation xml:lang="en">Return all RBD's, displayable and non-displayable.</xs:documentation>
                    </xs:annotation>
                </xs:enumeration>
            </xs:restriction>
        </xs:simpleType>
    </xs:attribute>
</xs:attributeGroup>