@Override
protected void internalPerform() throws AnalysisException {
//
// Build the standard HTML element.
//
HtmlUnitBuilder builder = new HtmlUnitBuilder(getContext());
element = builder.buildHtmlElement(source, modificationTime, unit);
final RecordingErrorListener errorListener = builder.getErrorListener();
//
// Validate the directives
//
unit.accept(new RecursiveXmlVisitor<Void>() {
@Override