SiteStructure structure = siteManager.getSiteStructure(getSourceDocument()
.getIdentityMap(), publication, getSourceDocument().getArea());
if (structure instanceof SiteTree) {
SiteTree tree = (SiteTree) structure;
SiteTreeNode node = tree.getNode(getSourceDocument().getId());
SiteTreeNode[] siblings = null;
String direction = getParameterAsString(DIRECTION);
if (direction.equals(UP)) {
siblings = node.getPrecedingSiblings();
} else if (direction.equals(DOWN)) {
siblings = node.getNextSiblings();
} else {
addErrorMessage("nudge-error-direction-unknown", new String[] { direction });
}
if (siblings != null && siblings.length == 0) {