for (int i = 0; i < children1.size(); i++) {
NLGElement child1 = children1.get(i);
NLGElement child2 = children2.get(i);
ElementCategory cat1 = child1.getCategory();
ElementCategory cat2 = child2.getCategory();
DiscourseFunction func1 = (DiscourseFunction) child1
.getFeature(InternalFeature.DISCOURSE_FUNCTION);
DiscourseFunction func2 = (DiscourseFunction) child2
.getFeature(InternalFeature.DISCOURSE_FUNCTION);
if (cat1 == cat2 && func1 == func2) {
pairs.add(FunctionalSet.newInstance(func1, cat1, periph,
child1, child2));