Correct validation of schema type QName

[Jeehong Min]

I am wondering if the Value attribute of StatusCode is valid according to the schema:   instance doc:  <Response           InResponseTo="ID_d03037d8-e25a-44dc-a6c2-5195ee3e8d13"           IssueInstant="2004-03-05T15:28:51.490Z"           MajorVersion="1"           MinorVersion="1"           ResponseID="ID_e6e8c8e6-d7a4-42e1-8020-b7825e3752fe"           xmlns="urn:oasis:names:tc:SAML:1.0:protocol">   <Status>    <StatusCode Value="samlp:Success"/>   </Status> ... </Response>   schema:        <element name="StatusCode" type="samlp:StatusCodeType"/>        <complexType name="StatusCodeType">                <sequence>                        <element ref="samlp:StatusCode" minOccurs="0"/>                </sequence>                <attribute name="Value" type="QName" use="required"/>        </complexType>   Note that attribute Value is of type QName.  Currently, my XML validator (based on Xerces of course) throws an error saying:   - cvc-attribute.3: The value 'samlp:Success' of attribute 'Value' on element 'StatusCode' is not valid with respect to its type. - UndeclaredPrefix: Cannot resolve 'samlp:Success' as a QName: the prefix 'samlp' is not declared. Does the QName have to be resolveable in the instance document or does it merely have to be a "valid" QName, where a "valid" QName has a prefix, a local part, and a namespace URI?   Thanks,   Jeehong Min