if (elem == null) {
// missing, we add it
elem = xmlDoc.getRootElement().addElement(
new QName(KEYWORD_MODIFIED, namespaceDcTerms));
} else {
elem.clearContent();// clear the old value
}
elem.addAttribute(new QName("type", namespaceXSI), "dcterms:W3CDTF");
elem.addText(propsPart.getModifiedPropertyString());
}