@Override
                public double distance(Comparison inProgress, EObject a, EObject b) {
                    EObject leftParent = a;
                    do {
                        leftParent = leftParent.eContainer();
                        Match match = inProgress.getMatch(leftParent);
                        if (match != null && match.getRight() == null) {
                            // no right match, assume it is part of a later ADDITION
                            return Double.MAX_VALUE;
                        }
                    } while (leftParent != null);
                    return super.distance(inProgress, a, b);
                }