public var test:XML;

private function initapp():void {
test = new XML(
'<clients>' +
  '<client user_id="5">' + 
'<username>bob</username>' + 
  '</client>' + 
  '<client user_id="6">' +
'<username>joe</username>' + 
  '</client>' + 
'</clients>');

delete (test..client.(username=="bob"));

trace(test);


}