}
@Override
public Object getValueAt(int rowIndex, int columnIndex) {
if (data == null) return null;
RelationToChildReference ref = data.get(rowIndex);
switch(columnIndex) {
case 0: return ref.getChild();
case 1: return ref.getParent();
case 2: return ref.getPosition()+1;
case 3: return ref.getRole();
default:
assert false: "Illegal column index";
}
return null;
}