first, thank you very much for responding, but still I have the impression that bottom refers to the more fundamental perspective, and top refers to the more g

first, thank you very much for responding, but still I have the impression that bottom refers to the more fundamental perspective, and top refers to the more general perspective... i.e. the fundamental equations for electromagnetism are the maxwell equations with epsilon, mu and c for vacuum, and then one can use these as microscopic equation for other media and generate effective equations for other media so that the new maxwell equations are similar but modified, i.e. different scalar epsilon, mu, c or perhaps for birefringent crystals the epsilon and mu are genralized to matrices/tensors, or for nonlinear optics theres second and third order tensors... and those new effective equations are top and the fundamental is bottom... at least thats how I think most people would denote top and bottom... I kind of see what you mean, but I don't think top annd bottom on energy scales is very significant, I think the derivabilitiy of new effective constitutive equations/propeerties from fundamental equations/properties is more top vs bottom... but I agree, at a certain point its not a discussion of physics but just dictionary wars...