* need to be re-analyzed each time they're referenced.
*
*/
private void buildChangePairsMap() {
if (_changePairsMap == null || _changePairsMap.isEmpty()) {
Defaults defaults = _root.getDefaults();
if (defaults != null) {
List<Property> properties = defaults.getProperty();
if (!properties.isEmpty()) {
_defaultProperties = new HashMap<String, Property>(properties.size(), 1);
for (Property prop : properties) {
_defaultProperties.put(prop.getKey(), prop);
}