// invalidate changed tuples, add them all to the focus set
focus.clear();
for ( int i=0; i<add.length; ++i ) {
((VisualItem)add[i]).setValidated(false);
focus.addTuple(add[i]);
}
for ( int i=0; i<rem.length; ++i ) {
((VisualItem)rem[i]).setValidated(false);
focus.addTuple(rem[i]);
}