}
// if necessary, insert a negative example (i.e. a tuple that does not pass the filter)
if (outputData.cardinality() == inputData.cardinality()) { // all tuples pass the filter; generate one input that will not pass the filter
ExampleTuple inputConstraint = new ExampleTuple();
Tuple inputConst = GenerateMatchingTuple(inputSchema, new NotCond(filterCond));
//inputConstraint.copyFrom(inputConst);
if (inputConst != null) {
inputConstraint.copyFrom(inputConst);
inputConstraints.add(inputConstraint);
}