*/
public AdditionalHeaderDefinition(XMLDocument doc) {
if (doc == null) {
throw new IllegalArgumentException("The header definition XML document cannot be null");
}
doc.gotoRoot().forEachChild(new CallBack() {
public void execute(XMLDocument doc) {
final String type = doc.getCurrentTagName().toLowerCase();
HeaderDefinition definition = definitions.get(type);
if (definition == null) {
definition = new HeaderDefinition(type);