Uri uri = namespace.getUri(token, parentUri);
Store store = uri.getStore();
if (!store.isSequenceSupported()) {
return null;
} else {
if (!store.sequenceExists(sequenceName)) {
store.createSequence(sequenceName);
}
long next = store.nextSequenceValue(sequenceName);
String uniqueUri = parentUri + "/" + next;
return uniqueUri;