<xs:element name="substeps">
    <xs:complexType>
        <xs:sequence>
            <xs:element maxOccurs="unbounded" ref="docbook:step" />
        </xs:sequence>
        <xs:attribute name="role" />
        <xs:attributeGroup ref="docbook:db.common.attributes" />
        <xs:attributeGroup ref="docbook:db.common.linking.attributes" />
        <xs:attribute name="performance">
            <xs:simpleType>
                <xs:restriction base="xs:token">
                    <xs:enumeration value="optional" />
                    <xs:enumeration value="required" />
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
    </xs:complexType>
</xs:element>