Document document = dbf.newDocumentBuilder().newDocument();
DocumentFragment fragment = document.createDocumentFragment();
Element x = document.createElementNS(null, "x");
Element y = document.createElementNS(null, "y");
fragment.appendChild(x);
fragment.appendChild(y);
Element element = document.createElementNS(null, "parent");
Element a = document.createElementNS(null, "a");
Element b = document.createElementNS(null, "b");