periodName.add(new UniqueDataFieldValidator<String>(Period.class, "name").limitScope("site", ISISession.get().getCurrentSiteModel()));
periodName.add(new SimpleAttributeModifier("maxlength", "32"));
periodName.setRequired(true);
periodName.setOutputMarkupId(true);
final FeedbackPanel feedback = new FeedbackPanel("feedback", new ContainerFeedbackMessageFilter(this));
feedback.setMaxMessages(1);
feedback.setOutputMarkupId(true);
add(feedback);
add(new AjaxFallbackLink<Object>("cancel") {