derived types in instance documents

[Jeehong Min]

All,   I have the following types defined in a schema:    <xsd:complexType name="AttributedString">   <xsd:simpleContent>    <xsd:extension base="xsd:string">     <xsd:attribute ref="wsu:Id"/>     <xsd:anyAttribute namespace="##other" processContents="lax"/>    </xsd:extension>   </xsd:simpleContent>  </xsd:complexType>  <xsd:complexType name="EncodedString">   <xsd:simpleContent>    <xsd:extension base="wsse:AttributedString">     <xsd:attribute name="EncodingType" type="xsd:anyURI"/>    </xsd:extension>   </xsd:simpleContent>  </xsd:complexType>  <xsd:complexType name="UsernameTokenType">   <xsd:sequence>    <xsd:element name="Username" type="wsse:AttributedString"/>    <xsd:any processContents="lax" minOccurs="0" maxOccurs="unbounded"/>   </xsd:sequence>   <xsd:attribute ref="wsu:Id"/>   <xsd:anyAttribute namespace="##other" processContents="lax"/>  </xsd:complexType> Note that EncodedString is derived from AttributedString.   The following passes XML Validation:    <ns1:UsernameToken>   <ns1:Username xsi:type="ns1:AttributedString" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> my username</ns1:Username>  </ns1:UsernameToken> And so does this:    <ns1:UsernameToken>   <ns1:Username>my username</ns1:Username>  </ns1:UsernameToken>   But Xerces throws an error on the following:    <ns1:UsernameToken>   <ns1:Username EncodingType="someType" xsi:type="ns1:EncodedString" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">my username</ns1:Username>  </ns1:UsernameToken> Xerces says:   cvc-elt.4.3: Type 'ns1:EncodedString' is not validly derived from the type definition, 'AttributedString', of element 'ns1:Username'.   It's not clear to me what is wrong with the XML.  Can someone shed some light?    Thanks. -- Jeehong Min Software Engineer SOAPtest Development Parasoft Corporation   "We Make Software Work"