@Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Delta<T> other = (Delta) obj;
        if (original == null) {
            if (other.original != null)
                return false;
        } else if (!original.equals(other.original))
            return false;
        if (revised == null) {
            if (other.revised != null)
                return false;
        } else if (!revised.equals(other.revised))
            return false;
        return true;
    }