<xs:attribute name="xpath" use="required">
    <xs:simpleType>
        <xs:annotation>
            <xs:documentation>A subset of XPath expressions for use
in fields</xs:documentation>
            <xs:documentation>A utility type, not for public
use</xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:token">
            <xs:annotation>
                <xs:documentation>The following pattern is intended to allow XPath
                           expressions per the same EBNF as for selector,
                           with the following change:
          Path    ::=    ('.//')? ( Step '/' )* ( Step | '@' NameTest ) 
         </xs:documentation>
            </xs:annotation>
            <xs:pattern value="(\.//)?((((child::)?((\i\c*:)?(\i\c*|\*)))|\.)/)*((((child::)?((\i\c*:)?(\i\c*|\*)))|\.)|((attribute::|@)((\i\c*:)?(\i\c*|\*))))(\|(\.//)?((((child::)?((\i\c*:)?(\i\c*|\*)))|\.)/)*((((child::)?((\i\c*:)?(\i\c*|\*)))|\.)|((attribute::|@)((\i\c*:)?(\i\c*|\*)))))*">
            </xs:pattern>
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>