handle

               The handle attribute allows a client application
               to assign a client-generated identifier for the 
               Query.  The handle is included to facilitate error
               reporting.  If one Query in a GetFeature request
               causes an exception, a WFS may report the handle
               to indicate which query element failed.  If the a
               handle is not present, the WFS may use other means
               to localize the error (e.g. line numbers).