<xs:attribute name="xpath" use="required">
    <xs:simpleType>
        <xs:annotation>
            <xs:documentation>A subset of XPath expressions for use
in selectors</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 following EBNF:
          Selector    ::=    Path ( '|' Path )*  
          Path    ::=    ('.//')? Step ( '/' Step )*  
          Step    ::=    '.' | NameTest  
          NameTest    ::=    QName | '*' | NCName ':' '*'  
                           child:: is also allowed
         </xs:documentation>
            </xs:annotation>
            <xs:pattern value="(\.//)?(((child::)?((\i\c*:)?(\i\c*|\*)))|\.)(/(((child::)?((\i\c*:)?(\i\c*|\*)))|\.))*(\|(\.//)?(((child::)?((\i\c*:)?(\i\c*|\*)))|\.)(/(((child::)?((\i\c*:)?(\i\c*|\*)))|\.))*)*">
            </xs:pattern>
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>