<xsd:complexType name="MetadataURLType">
    <xsd:annotation>
        <xsd:documentation>
            A Web Feature Server MAY use zero or more MetadataURL
            elements to offer detailed, standardized metadata about
            the data underneath a particular feature type.  The type
            attribute indicates the standard to which the metadata
            complies; the format attribute indicates how the metadata is
            structured.  Two types are defined at present:
            'TC211' or 'ISO19115' = ISO TC211 19115; 
            'FGDC'                = FGDC CSDGM.
            'ISO19139'            = ISO 19139
         </xsd:documentation>
    </xsd:annotation>
    <xsd:simpleContent>
        <xsd:extension base="xsd:string">
            <xsd:attribute name="type" use="required">
                <xsd:simpleType>
                    <xsd:restriction base="xsd:NMTOKEN">
                        <xsd:enumeration value="TC211" />
                        <xsd:enumeration value="FGDC" />
                        <xsd:enumeration value="19115" />
                        <xsd:enumeration value="19139" />
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:attribute>
            <xsd:attribute name="format" use="required">
                <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                        <!--  base="xsd:NMTOKEN"  "text/xml" is invalid wrt NMTOKEN -->
                        <xsd:enumeration value="text/xml" />
                        <xsd:enumeration value="text/html" />
                        <xsd:enumeration value="text/sgml" />
                        <xsd:enumeration value="text/plain" />
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:attribute>
        </xsd:extension>
    </xsd:simpleContent>
</xsd:complexType>

• MetadataURLType
• wfs:MetadataURL