loop:
while ( rightTuple != null && rightTuple.getPropagationContext() == pctx ) {
switch( rightTuple.getPropagationContext().getType() ) {
case PropagationContext.INSERTION:
case PropagationContext.RULE_ADDITION:
rightTuples.addInsert( rightTuple );
break;
case PropagationContext.MODIFICATION:
rightTuples.addUpdate( rightTuple );
break;
case PropagationContext.DELETION: