How to validate an element rather than the whole xml document

[Gloria Yang]

Dear all:       I need to validate an element aganist schema rather than the whole document.       For example, there is an SOAP message with element <key> as subelement.     and there is a key.xsd file specifies the data structure of element <key>       <SOAPENV:Envelope>         <SOAPBODY:Body>             <key>                   ....               </key>         </SOAPBODY:Body>     </SOAPENV:Envelope>       when I validate the SOAP message, xerces will bot validate content of <key> element against key.xsd.     Also after I validate the SOAP message, I will get a DOM tree.     How to make xerces to validate content of <key> element against key.xsd and not parse again?       Thank you. It's kind to show some examples.   Gloria