Besides the four density-based frameworks outlined above, which are in terms of either density associated quantities such as gradient and Laplacian, or different forms of density functionals and functional derivatives, is it possible to introduce and leverage other forms for our purpose? Also, how many physiochemical properties can we conceptualize? Is there a complete set? More importantly, same as the one-to-one mapping between the ground state density and external potential governed by the two basic theorems of DFT, is it possible to establish a similar mapping between an item in the density-based function space and a quantity in the physio-chemical property space? These are all open questions.