protected List<Set<Rule>> buildRuleSets() {
List<Set<Rule>> ls = new ArrayList<Set<Rule>>();
Set<Rule> s = new HashSet<Rule>();
// add split filter rule
Rule r = new LoadTypeCastInserter( "TypeCastInserter" );
s.add(r);
ls.add(s);
s = new HashSet<Rule>();
r = new PushDownForEachFlatten( "PushDownForEachFlatten" );