In this aproach, everything that works in old functionals is kept, while adding ability. It’s built up like a ladder in different steps. It represents 5 rungs that lead up to the ‘devine functional’, with which all problems could be solved. The first rung is LDA, the next are GGA’s, now the community is working on the 3rd rung: meta GGA’s,… By adding more complexity in each step, you come closer to an exact ‘devine functional’.