protected Collection verify(final MetaDataValue value, final String path) {
final Collection errors = super.verify(value, path);
if (value instanceof ListValue) {
// check unique member constraint
if (uniqueMemberConstraint != null) {
final ListValue list = (ListValue) value;
final Set values = new HashSet();
final Iterator iter = list.getContentsAsList().iterator();
for (int i = 1; iter.hasNext(); i++) {
final MetaDataValue child = (MetaDataValue) iter.next();
if (!values.add(child)) {
errors.add(new VerificationError(
VerificationError.TYPE_CONSTRAINT_VIOLATION,