After a nice black-board talk by Bovy about quasar target selection, he, Hennawi (visiting from MPIA), and I worked out a more general photometric redshift framework that could be applied to galaxies or quasars or anything else. It involves expanding the photometric space up to a much larger-dimensional spectrum space, and then, at each redshift, for each band, the observation is a projection of the high-dimensional space (plus noise). For any individual object there is no non-degenerate fit in the higher-dimensional space, but as long as there is large redshift-diversity, a collection of galaxies can constrain a prior on the spectrum space that would make the redshift inference optimally hierarchical. Love it! But it won't be easy to implement.